Alasdair Dempsey | Murdoch University (original) (raw)

Books by Alasdair Dempsey

Anterior cruciate ligament (ACL) rupture is a serious and debilitating injury that usually result... more Anterior cruciate ligament (ACL) rupture is a serious and debilitating injury that usually results in an athlete undergoing reconstructive surgery and remaining out of sport for an extended period. Therefore the incidence of this injury although only moderate (approximately one per professional Australian football team per year) when considered from a social and sporting cost perspectives is of serious concern. However, the non-contact nature of the majority of occurrences of this injury indicates that it may be possible to reduce the incidence with interventions aimed at modifying the movement and/or physical characteristics of individual athletes. Previous research aimed at reducing the risk of non-contact ACL injury has focused on improving support of general knee loads, particularly valgus and internal rotation moments, which are known to load the ACL, during sporting tasks through the utilisation of balance and plyometric training. While technique cues have been included in a number of these training programs there has been no research that has investigated training to change isolated aspects of sidestep cutting and landing techniques and their effect on valgus and internal rotation moments at the knee, the moments thought to cause non-contact ACL injury. This was the overarching theme of this thesis.

Most non-contact ACL injuries occur during either sidestep cutting or landing tasks, as such, the relationship between technique and knee loads was investigated within these two tasks. The first study presented in this thesis investigated how performing sidestep cuts with various extreme postures affected knee moments. It was identified that peak valgus loads during the weight acceptance phase of the sidestep cut were increased when performed with either increased torso lean over the support leg or wide placement of the support leg. Wide foot placement also resulted in increase peak internal rotation moments. Sidestep cuts, with torso rotation towards the support leg also increased peak knee internal rotation moments. As these postures were reflective of those observed during actual non-contact ACL injuries it was concluded that these three postures should be avoided when performing a sidestep cut.
The next study investigated the effectiveness of a six week technique modification program aimed at avoiding the three high loading techniques, identified in the first study, for reducing knee moments during sidestep cutting. Following the intervention participants performed the sidestep cut with a foot placement closer to the midline of the body and a more upright torso. These kinematic changes were accompanied by a reduction in the peak valgus moment occurring during the weight acceptance phase of the sidestep cut. This intervention may then reduce at least one factor identified as being a risk for an athlete of sustaining a non-contact ACL injury.

Studies three and four investigated the relationship between technique and knee loads during landing tasks. The first of these two studies investigated the effect of ball positioning in a functional landing task on both full body kinematics and knee moments. When participants were required to take possession of a ball during flight that was swinging towards their support leg they demonstrated increased valgus moments compared with when the ball was swung away from the support leg. The whole body segmental kinematics of the high loading ball movement reflected body postures observed when injury occurs in a game situation. However, the high loading task exhibited a more flexed knee posture, contrary to the results expected from the literature. The second of these two studies further investigated the relationship between whole body kinematics and knee moments. Intra-participant correlations were performed between all kinematics and each knee joint moment, with the intention of identifying mean correlations significantly different from zero. Increased valgus moments were significantly correlated with increased knee flexion, hip flexion, torso lean and torso rotation towards the support leg, and foot and knee external rotation. Increase internal rotation moments were significantly correlated with reduced hip abduction and external rotation, increased ankle inversion, knee external rotation and torso lean away from the support leg. Again these results reflected joint positions observed in injury, except for knee flexion and hip flexion angles. It was identified that while there may be statistically significant effects for knee angle the difference in magnitude may not result in functional differences.

The final study investigated the effect of a six week technique modification program on landing tasks. The technique modification aimed at bringing athletes’ torsos upright and forward facing, based upon the results of the previous studies. It also aimed to increase knee flexion angle, as this is still the current literature recommendation. Post-intervention participants displayed an increase in maximal knee flexion angles but no change in torso positioning. This kinematic change was correlated to a significant increase in peak internal rotation moments, with no change in valgus or flexion moments. Although, due to the angle at which the peak internal rotation moment occurred it was identified that this increase in moment may not increase the risk of non-contact ACL injury risk, due to the increased potential for muscular support and decreased transmission of the moment to the ACL. However, it was concluded that the technique modification program may not be appropriate for reducing the risk of non-contact ACL injury, within the particular landing task chosen.

Overall this thesis identified that whole body kinematics are related to knee moments during sidestep cutting and landing. Kinematics associated with increase valgus and internal rotation moments at the knee tended to reflect joint posture observed during actual non-contact ACL injuries. Secondly a six week technique modification program is capable of modifying both sidestep cutting and landing technique. Technique changes result in changed knee moments. However, the complex nature of the relationship between technique and knee loads indicates that any potential intervention aimed at reducing the risk of non-contact ACL injury, should be tested in the laboratory utilising tools such as neuromuscular modelling and stochastic modelling to ensure the planned intervention has the potential to be successful prior to implementing the protocol in an epidemiological testing scenario.

Papers by Alasdair Dempsey

Expertise studies into visual perceptual-motor skills have mainly focused their investigation up... more Expertise studies into visual perceptual-motor skills
have mainly focused their investigation upon group comparisons rather than individual comparisons. This study investigated the pick-up of visual information to time weight transfer
and bat kinematics within an exemplar group of striking sport
experts using an in situ temporal occlusion paradigm. Highly
skilled cricket batsmen faced bowlers and attempted to strike
delivered balls, whilst their vision was either temporally occluded
through occlusion glasses prior to ball bounce or not
occluded (control condition). A chronometric analysis was
conducted on trials in the occlusion condition to quantify the
pick-up of visual information to time biomechanical variables.
Results indicated that initiation of weight transfer and bat
downswing, as well as bat downswing completion, was significantly different between some individual batsmen. No significant difference was found between individual batsmen for time of weight transfer completion. Unexpectedly, it was
found that achievement of the goal to strike delivered balls,
that is, the frequency of bat-ball contacts was not significantly
different between batsmen. Collectively, the findings indicate
that individual differences exist in the coordination pattern of
a complex whole body visual perceptual-motor skill, but these
different patterns are used to achieve a similar outcome, which
is known as motor equivalence.

Keywords: Individual differences . Visual perceptual-motor
skill . Motor equivalence . Striking sports

Neurorehabilitation and neural repair, Jan 22, 2015

Background. The mirror neuron network provides a neural mechanism to prime the motor system throu... more Background. The mirror neuron network provides a neural mechanism to prime the motor system through action observation in stroke survivors. Objective. To examine whether action observation training with immediate physical practice improves upper-limb function in chronic stroke. Methods. In a within-subject design, 14 chronic stroke survivors were assessed at baseline, then participated in 2 weeks of relaxation-sham plus physical practice (control) and reassessed. Thereafter, they participated in 2 weeks of action observation training coupled with immediate physical practice (intervention), followed by a final assessment. Duration of each action observation video sequence (priming exposure) was 30 s followed immediately by practice of the observed motor skill. Results. There were significant improvements in control and intervention phases on primary outcome measures-Upper Extremity Fugl-Meyer Motor Assessment (FMA) and Functional Test of the Hemiparetic Upper Extremity (FTHUE)-as wel...

Objective: To explore the bivariate and multivariate relations between fatty degeneration of the ... more Objective: To explore the bivariate and multivariate relations between fatty degeneration of the lumbar multifidus muscle (LMM) and LMM function among patients with low back pain (LBP). Design: Cross-sectional clinical study. Setting: Hospital. Participants: Patients with LBP (NZ70) referred for lumbar spine magnetic resonance imaging. Interventions: Not applicable. Main Outcome Measures: LMM morphology and function were measured at the L4/L5 and L5/S1 spinal levels bilaterally. Quantitative measures of LMM intramuscular adipose tissue (IMAT) were derived from T1-weighted magnetic resonance images. Function was assessed with ultrasound imaging by measuring change in LMM thickness during a submaximal contraction task. The study participants self-reported their level of LBP-related disability (Modified Oswestry Index), pain intensity (numerical pain rating scale), and physical activity (International Physical Activity Questionnaire). Bivariate and multivariate relations between LMM morphology and function were explored with correlational and hierarchical linear regression analyses, respectively. Additionally, we explored for possible covariates with potential to modify the relation between LMM IMAT and function. Results: There were 70 participants (12 women) enrolled in the study (mean age, 45.4AE11.9y). A high level of physical activity was reported by 45.5% of participates. Age, sex, and physical activity level demonstrated variable relations with LMM IMAT and LMM function. There were no significant bivariate or multivariate relations between LMM IMAT and LMM function. Conclusions: We observed higher levels of physical activity and LMM function and less LMM IMAT than previous studies involving patients with LBP. There was no relation between LMM morphology and function in this cohort of patients with LBP. Issues specific to LMM measurement and recommendations for future research are discussed.

Clinical orthopaedics and related research, 2014

Knee muscle weakness and a greater external knee adduction moment are suggested risk factors for ... more Knee muscle weakness and a greater external knee adduction moment are suggested risk factors for medial tibiofemoral knee osteoarthritis. Knee muscle weakness and a greater knee adduction moment may be related to each other, are potentially modifiable, and have been observed after arthroscopic partial meniscectomy. The aim of this exploratory study was to determine if knee muscle weakness 3 months after arthroscopic partial meniscectomy (baseline) is associated with an increase in external knee adduction parameters during the subsequent 2 years. Eighty-two participants undergoing medial arthroscopic partial meniscectomy were assessed at baseline, and 66 participants who were reassessed 2 years later were included in our study. Isokinetic muscle strength and external adduction moment parameters (peak and impulse) during normal and fast walking were measured at baseline and followup. Multiple linear regression models were used to examine the association between baseline muscle strengt...

Clinical biomechanics (Bristol, Avon), 2014

Knee osteoarthritis is common following arthroscopic partial meniscectomy and a higher external p... more Knee osteoarthritis is common following arthroscopic partial meniscectomy and a higher external peak knee adduction moment is believed to be a contributor. The peak knee adduction moment has been shown to increase over 2 years (from 3-months post-arthroscopic partial meniscectomy). The aim of this study was to evaluate mechanisms underpinning the increase in peak knee adduction moment over 2 years observed in people 3-months following arthroscopic partial meniscectomy. Sixty-six participants with medial arthroscopic partial meniscectomy were assessed at baseline and again 2 years later. Parameters were evaluated at time of peak knee adduction moment as participants walked barefoot at their self-selected normal and fast pace for both time points. For normal pace walking, an increase in frontal plane ground reaction force-to-knee lever arm accounted for 30% of the increase in peak knee adduction moment (B=0.806 [95% CI 0.501-1.110], P<0.001). For fast pace walking, an increase in t...

Journal of biomechanics, Jan 22, 2014

People following arthroscopic partial medial meniscectomy (APM) are at increased risk of developi... more People following arthroscopic partial medial meniscectomy (APM) are at increased risk of developing knee osteoarthritis. High impact loading and peak loading early in the stance phase of gait may play a role in the pathogenesis of knee osteoarthritis. This was a secondary analysis of longitudinal data to investigate loading-related indices at baseline in an APM group (3 months post-surgery) and a healthy control group, and again 2 years later (follow-up). At baseline, 82 participants with medial APM and 38 healthy controls were assessed, with 66 and 23 re-assessed at follow-up, respectively. Outcome measures included: (i) heel strike transient (HST) presence and magnitude, (ii) maximum loading rate, (iii) peak vertical force (Fz) during early stance. At baseline, maximum loading rate was lower in the operated leg (APM) and non-operated leg (non-APM leg) compared to controls (p ≤ 0.03) and peak Fz was lower in the APM leg compared to non-APM leg (p ≤ 0.01). Over 2 years, peak Fz incr...

Objectives: Determine if balance and technique training (BTT) implemented adjunct to 1,001 male A... more Objectives: Determine if balance and technique training (BTT) implemented adjunct to 1,001 male Australian football (AF) players’ training influenced the activation/strength of the muscles crossing the knee during pre-planned (PpSS) and unplanned (UnSS) sidestepping. Design: Randomized Control Trial. Methods: Each AF player participated in either 28 weeks of BTT or ‘sham’ training (ST). Twenty-eight AF players (BTT, n = 12; ST, n = 16) completed biomechanical testing pre-to-post training. Peak knee moments and directed co-contraction ratios (DCCR) in three degrees of freedom, as well as total muscle activation were calculated during PpSS and UnSS. Results: No significant differences in muscle activation/strength were observed between the ST and BTT groups. Following a season of AF, knee extensor (p=0.023) and semimembranosus (p=0.006) muscle activation increased during both PpSS and UnSS. Following a season of AF, total muscle activation was 30% lower and peak valgus knee moments 80% greater (p=0.022) during UnSS when compared with PpSS. Conclusions: When implemented in a community level training environment, BTT was not effective in changing the activation of the muscles crossing the knee during sidestepping. Following a season of AF, players are better able to support both frontal and sagittal plane knee moments. When compared to PpSS, AF players may be at increased risk of ACL injury during UnSS in the latter half of an AF season.

Journal of Applied Biomechanics

Anterior cruciate ligament (ACL) injuries are costly. Sidestep technique training reduces knee m... more Anterior cruciate ligament (ACL) injuries are costly. Sidestep technique training reduces knee moments that load the ACL. This study examined whether landing technique training alters knee moments. Nineteen team sport athletes completed the study. Motion analysis and ground reaction forces were recorded before and after 6-weeks of technique modification. An inverse dynamic model was used to calculate three-dimensional knee loading. Pre- and post-intervention scores were compared using paired t-tests. Maximal knee flexion angle during landing was increased following training. There was no change in valgus or flexion moments, but an increase in peak internal rotation moment. This increase in internal rotation moment may increase the risk of ACL injury. However, the increased angle at which the peak internal rotation moment occurred at follow up may mitigate any increase in injury risk by reducing load transmission.

British Journal of Sports Medicine

BACKGROUND: Players are the targeted end-users and beneficiaries of exercise-training programm... more BACKGROUND:

Players are the targeted end-users and beneficiaries of exercise-training programmes implemented during coach-led training sessions, and the success of programmes depends upon their active participation. Two variants of an exercise-training programme were incorporated into the regular training schedules of 40 community Australian Football teams, over two seasons. One variant replicated common training practices, while the second was an evidence-based programme to alter biomechanical and neuromuscular factors related to risk of knee injuries. This paper describes the structure of the implemented programmes and compares players' end-of-season views about the programme variants.
METHODS:

This study was nested within a larger group-clustered randomised controlled trial of the effectiveness of two exercise-training programmes (control and neuromuscular control (NMC)) for preventing knee injuries. A post-season self-report survey, derived from Health Belief Model constructs, included questions to obtain players' views about the benefits and physical challenges of the programme in which they participated.
RESULTS:

Compared with control players, those who participated in the NMC programme found it to be less physically challenging but more enjoyable and potentially of more benefit. Suggestions from players about potential improvements to the training programme and its future implementation included reducing duration, increasing range of drills/exercises and promoting its injury prevention and other benefits to players.
CONCLUSIONS:

Players provide valuable feedback about the content and focus of implemented exercise-training programmes, that will directly inform the delivery of similar, or more successful, programmes in the future.

Medicine and Science in Sports and Exercise

Purpose: Individuals after arthroscopic partial medial meniscectomy (APM) are at increased risk o... more Purpose: Individuals after arthroscopic partial medial meniscectomy (APM) are at increased risk of developing knee osteoarthritis. Knee muscle weakness and a higher external knee adduction moment (KAM) are potential risk factors for knee osteoarthritis. This exploratory longitudinal study assessed these risk factors at baseline in an APM group (3 months after surgery) and control group, and again 2 years later (follow-up).

Methods: Eighty-two participants with medial APM and 38 healthy controls were assessed at baseline, with 66 (79%) and 23 (61%) respectively retested at follow-up. Outcome measures included isokinetic knee muscle strength and medial knee joint load inferred through indices of the KAM during normal and fast pace walking.

Results: Knee muscle strength was reduced by 14-16% in the APM leg compared to controls at baseline (p<=0.006). However, strength increased in the APM leg over the 2 years such that there were no differences compared with controls at follow-up. KAM impulse was at least 20% higher for the APM group (both legs) when compared to controls at baseline, and remained similarly higher 2 years later (p<=0.022). At baseline peak KAM was 18% higher in the APM leg as compared to controls only during fast pace walking (p=0.013). The peak KAM increased over the 2 years in the APM leg by 8-9% (p<=0.032), although there were no differences in change in KAM between the APM leg and controls.

Conclusion: This study found that while knee muscle strength improved, dynamic medial joint load increased over the 2-years following APM surgery. These findings may aid in developing therapeutic interventions aimed to prevent or delay the onset of knee osteoarthritis following APM.

Objectives: To compare physical activity levels, subject-reported function, and knee strength in ... more Objectives: To compare physical activity levels, subject-reported function, and knee strength in 21 arthroscopic partial meniscectomy (APM) patients (age 45.7 (6.06) years, BMI 27.3(5.96) Female 60%) 3 months post-surgery with 21 healthy controls (age 43.6 (5.71) years, BMI 24.5(4.2) Female 60%) matched at the cohort level for age, gender and BMI.
Design: Case control study
Methods: Physical activity intensity, number of steps, and minutes spent in activity were objectively quantified using an accelerometer-based activity monitor worn for 7 days. The Knee Injury and Osteoarthritis Outcome Score (KOOS) and concentric quadriceps strength were used to evaluate function post-surgery. Differences in activity levels and functional outcomes between the APM and control participants were assessed using t-tests, while multiple linear regression was used to quantify the best predictors of physical activity.
Results: APM patients engaged in a similar duration of activity to controls (469.0 (128.39) minutes vs. 497.1 (109.9) minutes), and take a similar number of steps per day (9227 (2977) vs. 10383 (3501), but performed their activity at lower levels of intensity than controls. Time spent in moderate (r2 = 0.19) and hard (r2 =0.145) intensity physical activity was best predicted by the Symptoms sub-scale of the KOOS for both controls and APM patients.
Conclusions: APM patients participate in similar activity however at a lower level, with the reduction in activity at higher intensities related to the presence of symptoms of knee osteoarthritis.

Purpose: To examine the relationship between tibiofemoral and patellofemoral joint articular cart... more Purpose: To examine the relationship between tibiofemoral and patellofemoral joint articular cartilage and subchondral bone in the medial and gait biomechanics following partial medial meniscectomy.
Methods: For this cross-sectional study, 122 patients aged 30-55 years, without evidence of knee osteoarthritis at arthroscopic partial medial meniscectomy, underwent gait analysis and MRI on the operated knee once for each sub-cohort of 3 months, 2 years, or 4 years post-surgery. Cartilage volume, cartilage defects, and bone size were assessed from the MRI using validated methods. The 1st peak in the knee adduction moment, knee adduction moment impulse, 1st peak in the knee flexion moment, knee extension range of motion, and the heel strike transient from the vertical ground reaction force trace were identified from the gait data.
Results: Increased knee stance phase range of motion was associated with decreased patella cartilage volume (B = -17.9 (95% CI-35.4, -0.4) p =0.045) while knee adduction moment impulse was associated with increased medial tibial plateau area (B = 7.7 (95% 0.9, 13.3) p = 0.025). A number of other variables approached significance.
Conclusions: Knee joint biomechanics exhibited by persons who had undergone arthroscopic partial meniscectomy gait may go some way to explaining the morphological degeneration observed at the patellofemoral and tibiofemoral compartments of the knee as patients progress from surgery.
Level of Evidence: III

Purpose Determine if balance and technique training (BTT) implemented adjunct to normal Australia... more Purpose Determine if balance and technique training (BTT) implemented adjunct to normal Australian football (AF) training reduces external knee loading during sidestepping. Additionally, the authors determined if an athlete's knee joint kinematics and kinetics change over a season of AF.

Methodology Eight amateur-level AF clubs (n=1,001 males) volunteered to participate in either 28 weeks of BTT or a ‘sham’ training (ST) adjunct to their normal preseason and regular training. A subset of 34 athletes (BTT, n=20; ST, n=14) were recruited for biomechanical testing in weeks 1–7 and 18–25 of the 28-week training intervention. During biomechanical testing, participants completed a series running, preplanned (PpSS) and unplanned sidestepping (UnSS) tasks. A linear mixed model (α=0.05) was used to determine if knee kinematics and peak moments during PpSS and UnSS were influenced by BTT and/or a season of AF.

Results Both training groups significantly (p=0.025) decreased their peak internal-rotation knee moments during PpSS, and significantly (p=0.022) increased their peak valgus knee moments during UnSS following their respective training interventions.

Conclusions BTT was not effective in changing an athlete's knee joint biomechanics during sidestepping when conducted in ‘real-world’ training environments. Following normal AF training, the players had different changes to their knee joint biomechanics during both preplanned and unplanned sidestepping. When performing an unplanned sidestepping task in the latter half of a playing season, athletes are at an increased risk of ACL injury. The authors therefore recommend both sidestepping tasks are performed during biomechanical testing when assessing the effectiveness of prophylactic training protocols.

Background: Athletes suffering an anterior cruciate ligament injury tend to exhibit similar body ... more Background: Athletes suffering an anterior cruciate ligament injury tend to exhibit similar body postures that in sidestep cutting are associated with increased knee moments. This relationship, however, has not been investigated in landing. Catching a ball in different overhead positions may affect landing postures and knee joint moments. This study investigated these possible relationships. It was anticipated that some joint postures would be associated increased knee loads during the landing task.
Methods: Twenty-five healthy male team sports athletes performed four variations of a landing task. Full body kinematics were identified at initial contact. Peak flexion, valgus and internal rotation moments at the knee, measured during early landing, were normalized to mass and height and statistically compared. Intra-participant correlations were performed between all kinematics and each moment. Mean slopes for each correlation were used to identify the existence of relationships between full body kinematics and knee joint moments.
Findings: Landing after an overhead catch when the ball moved towards a player’s support leg resulted in increased peak valgus moments. These increased valgus moments were correlated with increased knee flexion, hip flexion, and torso lean, as well as torso rotation towards the support leg, and foot and knee external rotation. Increased internal rotation moments were correlated with reduced hip abduction and external rotation, increased ankle inversion, knee external rotation and torso lean away from the support leg.
Interpretation: Learning to land with techniques that do not reflect postures associated with high knee moments may reduce an athlete’s risk of non-contact anterior cruciate ligament injury.

Purpose: To examine articular cartilage and subchondral bone changes in tibiofemoral and patellof... more Purpose: To examine articular cartilage and subchondral bone changes in tibiofemoral and patellofemoral joints following partial medial meniscectomy.

Methods: For this cross-sectional study, 158 patients aged 30-55 years, without evidence of knee osteoarthritis at arthroscopic partial medial meniscectomy (APMM), and 38 controls were recruited. MRI was performed once on the operated knee for each subcohort of 3 months, 2 years, or 4 years post-surgery, and the randomly assigned knee of the controls. Cartilage volume, cartilage defects, and bone size were assessed using validated methods.

Results: Compared with controls, APMM patients had more prevalent cartilage defects in medial tibiofemoral (OR=3.17, 95%CI 1.24-8.11) and patellofemoral (OR=13.76, 95%CI 1.52-124.80) compartments, and increased medial tibial plateau bone area (B=143.8, 95%CI 57.4-230.2). Time from APMM was positively associated with cartilage defect prevalence in medial tibiofemoral (OR=1.02, 95%CI 1.00-1.03) and patellofemoral (OR=1.04, 95%CI 1.01-1.07) compartments, and medial tibial plateau area (B=2.5, 95%CI 0.8-4.3), but negatively associated with lateral tibial cartilage volume (B=-4.9, 95%CI -8.4 to -1.5). The association of APMM and time from APMM with patellar cartilage defects was independent of tibial cartilage volume.

Conclusions: Partial medial meniscectomy is associated with adverse effects on articular cartilage and subchondral bone, which are associated with subsequent osteoarthritis, in both tibiofemoral and patellofemoral compartments.

The objective of this work is to evaluate differences in trabecular bone (TB) texture between sub... more The objective of this work is to evaluate differences in trabecular bone (TB) texture between subjects with and without tibiofemoral cartilage defects using a variance orientation transform (VOT) method. A case–control study was performed in subjects without radiographic knee OA (K&L grade<2) matched on sex, BMI, age, knee compartment and meniscectomy where cases (n=28) had cartilage defects (grade≥2) and controls (n=28) had no cartilage defects (grade<2). Cartilage defects were assessed from MRI using validated methods. The VOT was applied to TB regions selected on medial and lateral compartments in knee X-rays and fractal signatures (FS) in the horizontal ( ) and vertical ( ) directions, and along the roughest part of TB ( ) and texture aspect ratio signatures ( ), at different trabecular image sizes (0.30-0.70 mm) were calculated. Compared with controls, for cases were higher (P<0.011) at image sizes 0.30-0.40 mm and 0.45–0.55 mm in the medial compartment. In the lateral compartment, and for cases were higher (P<0.028) than those for controls at 0.30-0.40 mm and 0.45–0.55 mm, while was higher (P<0.02) at 0.30-0.40 mm. TB texture roughness was greater in subjects with cartilage defects than in subjects without, suggesting thinning and fenestration of TB occur early in OA and that the VOT identifies changes in TB in knees with early cartilage damage. No differences in (P>0.05) were found.

INTRODUCTION:: Prophylactic taping is commonly used to prevent ankle injuries during sports. Howe... more INTRODUCTION:: Prophylactic taping is commonly used to prevent ankle injuries during sports. However unnatural constraint of the ankle joint may increase the risk of injury to proximal joints such as the knee. The association between ankle taping and knee joint loading during open sporting tasks has not been quantified. This research aimed to measure changes in knee and ankle kinetics and kinematics during dynamic athletic activities undertaken with and without ankle taping

METHODS:: A kinematic and inverse dynamics model was used to determine ankle and knee joint motion and loading in 22 healthy male participants undertaking running and sidestepping tasks. Both tasks were randomized to planned and unplanned conditions, and undertaken with and without the use of ankle tape.

RESULTS:: At the knee, internal rotation moments (p=<0.001) and varus moments (p<0.05) were reduced for all tasks. Internal rotation impulse (p<0.001) was reduced for sidestepping tasks. Varus impulse during unplanned sidestepping maneuvers (p=0.04) was reduced with the use of ankle tape. However there was a trend toward increased valgus moments and impulse for planned sidestepping trials undertaken with ankle tape (p=0.056). Taping reduced the range of motion at the ankle in all three planes (p<0.05). Peak inversion (p<0.001) was reduced for running trials only. Average eversion and peak dorsiflexion moments were significantly reduced in sidestepping tasks by use of taping.

CONCLUSION:: By limiting motion at the ankle, taping increased mechanical stability at this joint. Ankle taping also provided protective benefits to the knee via reduced internal rotation moments and varus impulses during both planned and unplanned maneuvers. Medial collateral and anterior cruciate ligament injuries may, however, occur through increased valgus impulse during sidestepping undertaken with ankle tape.

Background: Common lower limb postures have been found when noncontact anterior cruciate ligament... more Background: Common lower limb postures have been found when noncontact anterior cruciate ligament (ACL) injuries occur during sidestep cutting tasks. These same postures have been linked to knee loadings known to stress the ACL.
Hypothesis: Whole body technique modification would reduce knee loading.

Study Design: Controlled laboratory study.

Methods: Experienced team sport athletes were recruited for whole body sidestep cutting technique modification. Before and
after a 6-week technique modification training, participants performed sidestep cutting tasks while ground-reaction force and motion data were collected. A kinematic and inverse dynamics model was used to calculate 3-dimensional knee loading during sidestep cutting.

Results: At initial foot contact, the participants placed their stance foot closer to the body’s midline and held their torso more upright, in line with the aims of the technique modification training. This was accompanied by significantly lower peak valgus moments in the weight acceptance phase of stance. Both postural changes were correlated with the change in peak valgus moment.

Conclusion: Whole body sidestep cutting technique modification resulted in reduced knee loading.

Clinical Relevance: Implementation of whole body technique modification may produce effective ACL injury prevention programs in sports involving sidestep cutting.

Anterior cruciate ligament (ACL) rupture is a serious and debilitating injury that usually result... more Anterior cruciate ligament (ACL) rupture is a serious and debilitating injury that usually results in an athlete undergoing reconstructive surgery and remaining out of sport for an extended period. Therefore the incidence of this injury although only moderate (approximately one per professional Australian football team per year) when considered from a social and sporting cost perspectives is of serious concern. However, the non-contact nature of the majority of occurrences of this injury indicates that it may be possible to reduce the incidence with interventions aimed at modifying the movement and/or physical characteristics of individual athletes. Previous research aimed at reducing the risk of non-contact ACL injury has focused on improving support of general knee loads, particularly valgus and internal rotation moments, which are known to load the ACL, during sporting tasks through the utilisation of balance and plyometric training. While technique cues have been included in a number of these training programs there has been no research that has investigated training to change isolated aspects of sidestep cutting and landing techniques and their effect on valgus and internal rotation moments at the knee, the moments thought to cause non-contact ACL injury. This was the overarching theme of this thesis.

Most non-contact ACL injuries occur during either sidestep cutting or landing tasks, as such, the relationship between technique and knee loads was investigated within these two tasks. The first study presented in this thesis investigated how performing sidestep cuts with various extreme postures affected knee moments. It was identified that peak valgus loads during the weight acceptance phase of the sidestep cut were increased when performed with either increased torso lean over the support leg or wide placement of the support leg. Wide foot placement also resulted in increase peak internal rotation moments. Sidestep cuts, with torso rotation towards the support leg also increased peak knee internal rotation moments. As these postures were reflective of those observed during actual non-contact ACL injuries it was concluded that these three postures should be avoided when performing a sidestep cut.
The next study investigated the effectiveness of a six week technique modification program aimed at avoiding the three high loading techniques, identified in the first study, for reducing knee moments during sidestep cutting. Following the intervention participants performed the sidestep cut with a foot placement closer to the midline of the body and a more upright torso. These kinematic changes were accompanied by a reduction in the peak valgus moment occurring during the weight acceptance phase of the sidestep cut. This intervention may then reduce at least one factor identified as being a risk for an athlete of sustaining a non-contact ACL injury.

Studies three and four investigated the relationship between technique and knee loads during landing tasks. The first of these two studies investigated the effect of ball positioning in a functional landing task on both full body kinematics and knee moments. When participants were required to take possession of a ball during flight that was swinging towards their support leg they demonstrated increased valgus moments compared with when the ball was swung away from the support leg. The whole body segmental kinematics of the high loading ball movement reflected body postures observed when injury occurs in a game situation. However, the high loading task exhibited a more flexed knee posture, contrary to the results expected from the literature. The second of these two studies further investigated the relationship between whole body kinematics and knee moments. Intra-participant correlations were performed between all kinematics and each knee joint moment, with the intention of identifying mean correlations significantly different from zero. Increased valgus moments were significantly correlated with increased knee flexion, hip flexion, torso lean and torso rotation towards the support leg, and foot and knee external rotation. Increase internal rotation moments were significantly correlated with reduced hip abduction and external rotation, increased ankle inversion, knee external rotation and torso lean away from the support leg. Again these results reflected joint positions observed in injury, except for knee flexion and hip flexion angles. It was identified that while there may be statistically significant effects for knee angle the difference in magnitude may not result in functional differences.

The final study investigated the effect of a six week technique modification program on landing tasks. The technique modification aimed at bringing athletes’ torsos upright and forward facing, based upon the results of the previous studies. It also aimed to increase knee flexion angle, as this is still the current literature recommendation. Post-intervention participants displayed an increase in maximal knee flexion angles but no change in torso positioning. This kinematic change was correlated to a significant increase in peak internal rotation moments, with no change in valgus or flexion moments. Although, due to the angle at which the peak internal rotation moment occurred it was identified that this increase in moment may not increase the risk of non-contact ACL injury risk, due to the increased potential for muscular support and decreased transmission of the moment to the ACL. However, it was concluded that the technique modification program may not be appropriate for reducing the risk of non-contact ACL injury, within the particular landing task chosen.

Overall this thesis identified that whole body kinematics are related to knee moments during sidestep cutting and landing. Kinematics associated with increase valgus and internal rotation moments at the knee tended to reflect joint posture observed during actual non-contact ACL injuries. Secondly a six week technique modification program is capable of modifying both sidestep cutting and landing technique. Technique changes result in changed knee moments. However, the complex nature of the relationship between technique and knee loads indicates that any potential intervention aimed at reducing the risk of non-contact ACL injury, should be tested in the laboratory utilising tools such as neuromuscular modelling and stochastic modelling to ensure the planned intervention has the potential to be successful prior to implementing the protocol in an epidemiological testing scenario.

Expertise studies into visual perceptual-motor skills have mainly focused their investigation up... more Expertise studies into visual perceptual-motor skills
have mainly focused their investigation upon group comparisons rather than individual comparisons. This study investigated the pick-up of visual information to time weight transfer
and bat kinematics within an exemplar group of striking sport
experts using an in situ temporal occlusion paradigm. Highly
skilled cricket batsmen faced bowlers and attempted to strike
delivered balls, whilst their vision was either temporally occluded
through occlusion glasses prior to ball bounce or not
occluded (control condition). A chronometric analysis was
conducted on trials in the occlusion condition to quantify the
pick-up of visual information to time biomechanical variables.
Results indicated that initiation of weight transfer and bat
downswing, as well as bat downswing completion, was significantly different between some individual batsmen. No significant difference was found between individual batsmen for time of weight transfer completion. Unexpectedly, it was
found that achievement of the goal to strike delivered balls,
that is, the frequency of bat-ball contacts was not significantly
different between batsmen. Collectively, the findings indicate
that individual differences exist in the coordination pattern of
a complex whole body visual perceptual-motor skill, but these
different patterns are used to achieve a similar outcome, which
is known as motor equivalence.

Keywords: Individual differences . Visual perceptual-motor
skill . Motor equivalence . Striking sports

Neurorehabilitation and neural repair, Jan 22, 2015

Background. The mirror neuron network provides a neural mechanism to prime the motor system throu... more Background. The mirror neuron network provides a neural mechanism to prime the motor system through action observation in stroke survivors. Objective. To examine whether action observation training with immediate physical practice improves upper-limb function in chronic stroke. Methods. In a within-subject design, 14 chronic stroke survivors were assessed at baseline, then participated in 2 weeks of relaxation-sham plus physical practice (control) and reassessed. Thereafter, they participated in 2 weeks of action observation training coupled with immediate physical practice (intervention), followed by a final assessment. Duration of each action observation video sequence (priming exposure) was 30 s followed immediately by practice of the observed motor skill. Results. There were significant improvements in control and intervention phases on primary outcome measures-Upper Extremity Fugl-Meyer Motor Assessment (FMA) and Functional Test of the Hemiparetic Upper Extremity (FTHUE)-as wel...

Objective: To explore the bivariate and multivariate relations between fatty degeneration of the ... more Objective: To explore the bivariate and multivariate relations between fatty degeneration of the lumbar multifidus muscle (LMM) and LMM function among patients with low back pain (LBP). Design: Cross-sectional clinical study. Setting: Hospital. Participants: Patients with LBP (NZ70) referred for lumbar spine magnetic resonance imaging. Interventions: Not applicable. Main Outcome Measures: LMM morphology and function were measured at the L4/L5 and L5/S1 spinal levels bilaterally. Quantitative measures of LMM intramuscular adipose tissue (IMAT) were derived from T1-weighted magnetic resonance images. Function was assessed with ultrasound imaging by measuring change in LMM thickness during a submaximal contraction task. The study participants self-reported their level of LBP-related disability (Modified Oswestry Index), pain intensity (numerical pain rating scale), and physical activity (International Physical Activity Questionnaire). Bivariate and multivariate relations between LMM morphology and function were explored with correlational and hierarchical linear regression analyses, respectively. Additionally, we explored for possible covariates with potential to modify the relation between LMM IMAT and function. Results: There were 70 participants (12 women) enrolled in the study (mean age, 45.4AE11.9y). A high level of physical activity was reported by 45.5% of participates. Age, sex, and physical activity level demonstrated variable relations with LMM IMAT and LMM function. There were no significant bivariate or multivariate relations between LMM IMAT and LMM function. Conclusions: We observed higher levels of physical activity and LMM function and less LMM IMAT than previous studies involving patients with LBP. There was no relation between LMM morphology and function in this cohort of patients with LBP. Issues specific to LMM measurement and recommendations for future research are discussed.

Clinical orthopaedics and related research, 2014

Knee muscle weakness and a greater external knee adduction moment are suggested risk factors for ... more Knee muscle weakness and a greater external knee adduction moment are suggested risk factors for medial tibiofemoral knee osteoarthritis. Knee muscle weakness and a greater knee adduction moment may be related to each other, are potentially modifiable, and have been observed after arthroscopic partial meniscectomy. The aim of this exploratory study was to determine if knee muscle weakness 3 months after arthroscopic partial meniscectomy (baseline) is associated with an increase in external knee adduction parameters during the subsequent 2 years. Eighty-two participants undergoing medial arthroscopic partial meniscectomy were assessed at baseline, and 66 participants who were reassessed 2 years later were included in our study. Isokinetic muscle strength and external adduction moment parameters (peak and impulse) during normal and fast walking were measured at baseline and followup. Multiple linear regression models were used to examine the association between baseline muscle strengt...

Clinical biomechanics (Bristol, Avon), 2014

Knee osteoarthritis is common following arthroscopic partial meniscectomy and a higher external p... more Knee osteoarthritis is common following arthroscopic partial meniscectomy and a higher external peak knee adduction moment is believed to be a contributor. The peak knee adduction moment has been shown to increase over 2 years (from 3-months post-arthroscopic partial meniscectomy). The aim of this study was to evaluate mechanisms underpinning the increase in peak knee adduction moment over 2 years observed in people 3-months following arthroscopic partial meniscectomy. Sixty-six participants with medial arthroscopic partial meniscectomy were assessed at baseline and again 2 years later. Parameters were evaluated at time of peak knee adduction moment as participants walked barefoot at their self-selected normal and fast pace for both time points. For normal pace walking, an increase in frontal plane ground reaction force-to-knee lever arm accounted for 30% of the increase in peak knee adduction moment (B=0.806 [95% CI 0.501-1.110], P<0.001). For fast pace walking, an increase in t...

Journal of biomechanics, Jan 22, 2014

People following arthroscopic partial medial meniscectomy (APM) are at increased risk of developi... more People following arthroscopic partial medial meniscectomy (APM) are at increased risk of developing knee osteoarthritis. High impact loading and peak loading early in the stance phase of gait may play a role in the pathogenesis of knee osteoarthritis. This was a secondary analysis of longitudinal data to investigate loading-related indices at baseline in an APM group (3 months post-surgery) and a healthy control group, and again 2 years later (follow-up). At baseline, 82 participants with medial APM and 38 healthy controls were assessed, with 66 and 23 re-assessed at follow-up, respectively. Outcome measures included: (i) heel strike transient (HST) presence and magnitude, (ii) maximum loading rate, (iii) peak vertical force (Fz) during early stance. At baseline, maximum loading rate was lower in the operated leg (APM) and non-operated leg (non-APM leg) compared to controls (p ≤ 0.03) and peak Fz was lower in the APM leg compared to non-APM leg (p ≤ 0.01). Over 2 years, peak Fz incr...

Objectives: Determine if balance and technique training (BTT) implemented adjunct to 1,001 male A... more Objectives: Determine if balance and technique training (BTT) implemented adjunct to 1,001 male Australian football (AF) players’ training influenced the activation/strength of the muscles crossing the knee during pre-planned (PpSS) and unplanned (UnSS) sidestepping. Design: Randomized Control Trial. Methods: Each AF player participated in either 28 weeks of BTT or ‘sham’ training (ST). Twenty-eight AF players (BTT, n = 12; ST, n = 16) completed biomechanical testing pre-to-post training. Peak knee moments and directed co-contraction ratios (DCCR) in three degrees of freedom, as well as total muscle activation were calculated during PpSS and UnSS. Results: No significant differences in muscle activation/strength were observed between the ST and BTT groups. Following a season of AF, knee extensor (p=0.023) and semimembranosus (p=0.006) muscle activation increased during both PpSS and UnSS. Following a season of AF, total muscle activation was 30% lower and peak valgus knee moments 80% greater (p=0.022) during UnSS when compared with PpSS. Conclusions: When implemented in a community level training environment, BTT was not effective in changing the activation of the muscles crossing the knee during sidestepping. Following a season of AF, players are better able to support both frontal and sagittal plane knee moments. When compared to PpSS, AF players may be at increased risk of ACL injury during UnSS in the latter half of an AF season.

Journal of Applied Biomechanics

Anterior cruciate ligament (ACL) injuries are costly. Sidestep technique training reduces knee m... more Anterior cruciate ligament (ACL) injuries are costly. Sidestep technique training reduces knee moments that load the ACL. This study examined whether landing technique training alters knee moments. Nineteen team sport athletes completed the study. Motion analysis and ground reaction forces were recorded before and after 6-weeks of technique modification. An inverse dynamic model was used to calculate three-dimensional knee loading. Pre- and post-intervention scores were compared using paired t-tests. Maximal knee flexion angle during landing was increased following training. There was no change in valgus or flexion moments, but an increase in peak internal rotation moment. This increase in internal rotation moment may increase the risk of ACL injury. However, the increased angle at which the peak internal rotation moment occurred at follow up may mitigate any increase in injury risk by reducing load transmission.

British Journal of Sports Medicine

BACKGROUND: Players are the targeted end-users and beneficiaries of exercise-training programm... more BACKGROUND:

Players are the targeted end-users and beneficiaries of exercise-training programmes implemented during coach-led training sessions, and the success of programmes depends upon their active participation. Two variants of an exercise-training programme were incorporated into the regular training schedules of 40 community Australian Football teams, over two seasons. One variant replicated common training practices, while the second was an evidence-based programme to alter biomechanical and neuromuscular factors related to risk of knee injuries. This paper describes the structure of the implemented programmes and compares players' end-of-season views about the programme variants.
METHODS:

This study was nested within a larger group-clustered randomised controlled trial of the effectiveness of two exercise-training programmes (control and neuromuscular control (NMC)) for preventing knee injuries. A post-season self-report survey, derived from Health Belief Model constructs, included questions to obtain players' views about the benefits and physical challenges of the programme in which they participated.
RESULTS:

Compared with control players, those who participated in the NMC programme found it to be less physically challenging but more enjoyable and potentially of more benefit. Suggestions from players about potential improvements to the training programme and its future implementation included reducing duration, increasing range of drills/exercises and promoting its injury prevention and other benefits to players.
CONCLUSIONS:

Players provide valuable feedback about the content and focus of implemented exercise-training programmes, that will directly inform the delivery of similar, or more successful, programmes in the future.

Medicine and Science in Sports and Exercise

Purpose: Individuals after arthroscopic partial medial meniscectomy (APM) are at increased risk o... more Purpose: Individuals after arthroscopic partial medial meniscectomy (APM) are at increased risk of developing knee osteoarthritis. Knee muscle weakness and a higher external knee adduction moment (KAM) are potential risk factors for knee osteoarthritis. This exploratory longitudinal study assessed these risk factors at baseline in an APM group (3 months after surgery) and control group, and again 2 years later (follow-up).

Methods: Eighty-two participants with medial APM and 38 healthy controls were assessed at baseline, with 66 (79%) and 23 (61%) respectively retested at follow-up. Outcome measures included isokinetic knee muscle strength and medial knee joint load inferred through indices of the KAM during normal and fast pace walking.

Results: Knee muscle strength was reduced by 14-16% in the APM leg compared to controls at baseline (p<=0.006). However, strength increased in the APM leg over the 2 years such that there were no differences compared with controls at follow-up. KAM impulse was at least 20% higher for the APM group (both legs) when compared to controls at baseline, and remained similarly higher 2 years later (p<=0.022). At baseline peak KAM was 18% higher in the APM leg as compared to controls only during fast pace walking (p=0.013). The peak KAM increased over the 2 years in the APM leg by 8-9% (p<=0.032), although there were no differences in change in KAM between the APM leg and controls.

Conclusion: This study found that while knee muscle strength improved, dynamic medial joint load increased over the 2-years following APM surgery. These findings may aid in developing therapeutic interventions aimed to prevent or delay the onset of knee osteoarthritis following APM.

Objectives: To compare physical activity levels, subject-reported function, and knee strength in ... more Objectives: To compare physical activity levels, subject-reported function, and knee strength in 21 arthroscopic partial meniscectomy (APM) patients (age 45.7 (6.06) years, BMI 27.3(5.96) Female 60%) 3 months post-surgery with 21 healthy controls (age 43.6 (5.71) years, BMI 24.5(4.2) Female 60%) matched at the cohort level for age, gender and BMI.
Design: Case control study
Methods: Physical activity intensity, number of steps, and minutes spent in activity were objectively quantified using an accelerometer-based activity monitor worn for 7 days. The Knee Injury and Osteoarthritis Outcome Score (KOOS) and concentric quadriceps strength were used to evaluate function post-surgery. Differences in activity levels and functional outcomes between the APM and control participants were assessed using t-tests, while multiple linear regression was used to quantify the best predictors of physical activity.
Results: APM patients engaged in a similar duration of activity to controls (469.0 (128.39) minutes vs. 497.1 (109.9) minutes), and take a similar number of steps per day (9227 (2977) vs. 10383 (3501), but performed their activity at lower levels of intensity than controls. Time spent in moderate (r2 = 0.19) and hard (r2 =0.145) intensity physical activity was best predicted by the Symptoms sub-scale of the KOOS for both controls and APM patients.
Conclusions: APM patients participate in similar activity however at a lower level, with the reduction in activity at higher intensities related to the presence of symptoms of knee osteoarthritis.

Purpose: To examine the relationship between tibiofemoral and patellofemoral joint articular cart... more Purpose: To examine the relationship between tibiofemoral and patellofemoral joint articular cartilage and subchondral bone in the medial and gait biomechanics following partial medial meniscectomy.
Methods: For this cross-sectional study, 122 patients aged 30-55 years, without evidence of knee osteoarthritis at arthroscopic partial medial meniscectomy, underwent gait analysis and MRI on the operated knee once for each sub-cohort of 3 months, 2 years, or 4 years post-surgery. Cartilage volume, cartilage defects, and bone size were assessed from the MRI using validated methods. The 1st peak in the knee adduction moment, knee adduction moment impulse, 1st peak in the knee flexion moment, knee extension range of motion, and the heel strike transient from the vertical ground reaction force trace were identified from the gait data.
Results: Increased knee stance phase range of motion was associated with decreased patella cartilage volume (B = -17.9 (95% CI-35.4, -0.4) p =0.045) while knee adduction moment impulse was associated with increased medial tibial plateau area (B = 7.7 (95% 0.9, 13.3) p = 0.025). A number of other variables approached significance.
Conclusions: Knee joint biomechanics exhibited by persons who had undergone arthroscopic partial meniscectomy gait may go some way to explaining the morphological degeneration observed at the patellofemoral and tibiofemoral compartments of the knee as patients progress from surgery.
Level of Evidence: III

Purpose Determine if balance and technique training (BTT) implemented adjunct to normal Australia... more Purpose Determine if balance and technique training (BTT) implemented adjunct to normal Australian football (AF) training reduces external knee loading during sidestepping. Additionally, the authors determined if an athlete's knee joint kinematics and kinetics change over a season of AF.

Methodology Eight amateur-level AF clubs (n=1,001 males) volunteered to participate in either 28 weeks of BTT or a ‘sham’ training (ST) adjunct to their normal preseason and regular training. A subset of 34 athletes (BTT, n=20; ST, n=14) were recruited for biomechanical testing in weeks 1–7 and 18–25 of the 28-week training intervention. During biomechanical testing, participants completed a series running, preplanned (PpSS) and unplanned sidestepping (UnSS) tasks. A linear mixed model (α=0.05) was used to determine if knee kinematics and peak moments during PpSS and UnSS were influenced by BTT and/or a season of AF.

Results Both training groups significantly (p=0.025) decreased their peak internal-rotation knee moments during PpSS, and significantly (p=0.022) increased their peak valgus knee moments during UnSS following their respective training interventions.

Conclusions BTT was not effective in changing an athlete's knee joint biomechanics during sidestepping when conducted in ‘real-world’ training environments. Following normal AF training, the players had different changes to their knee joint biomechanics during both preplanned and unplanned sidestepping. When performing an unplanned sidestepping task in the latter half of a playing season, athletes are at an increased risk of ACL injury. The authors therefore recommend both sidestepping tasks are performed during biomechanical testing when assessing the effectiveness of prophylactic training protocols.

Background: Athletes suffering an anterior cruciate ligament injury tend to exhibit similar body ... more Background: Athletes suffering an anterior cruciate ligament injury tend to exhibit similar body postures that in sidestep cutting are associated with increased knee moments. This relationship, however, has not been investigated in landing. Catching a ball in different overhead positions may affect landing postures and knee joint moments. This study investigated these possible relationships. It was anticipated that some joint postures would be associated increased knee loads during the landing task.
Methods: Twenty-five healthy male team sports athletes performed four variations of a landing task. Full body kinematics were identified at initial contact. Peak flexion, valgus and internal rotation moments at the knee, measured during early landing, were normalized to mass and height and statistically compared. Intra-participant correlations were performed between all kinematics and each moment. Mean slopes for each correlation were used to identify the existence of relationships between full body kinematics and knee joint moments.
Findings: Landing after an overhead catch when the ball moved towards a player’s support leg resulted in increased peak valgus moments. These increased valgus moments were correlated with increased knee flexion, hip flexion, and torso lean, as well as torso rotation towards the support leg, and foot and knee external rotation. Increased internal rotation moments were correlated with reduced hip abduction and external rotation, increased ankle inversion, knee external rotation and torso lean away from the support leg.
Interpretation: Learning to land with techniques that do not reflect postures associated with high knee moments may reduce an athlete’s risk of non-contact anterior cruciate ligament injury.

Purpose: To examine articular cartilage and subchondral bone changes in tibiofemoral and patellof... more Purpose: To examine articular cartilage and subchondral bone changes in tibiofemoral and patellofemoral joints following partial medial meniscectomy.

Methods: For this cross-sectional study, 158 patients aged 30-55 years, without evidence of knee osteoarthritis at arthroscopic partial medial meniscectomy (APMM), and 38 controls were recruited. MRI was performed once on the operated knee for each subcohort of 3 months, 2 years, or 4 years post-surgery, and the randomly assigned knee of the controls. Cartilage volume, cartilage defects, and bone size were assessed using validated methods.

Results: Compared with controls, APMM patients had more prevalent cartilage defects in medial tibiofemoral (OR=3.17, 95%CI 1.24-8.11) and patellofemoral (OR=13.76, 95%CI 1.52-124.80) compartments, and increased medial tibial plateau bone area (B=143.8, 95%CI 57.4-230.2). Time from APMM was positively associated with cartilage defect prevalence in medial tibiofemoral (OR=1.02, 95%CI 1.00-1.03) and patellofemoral (OR=1.04, 95%CI 1.01-1.07) compartments, and medial tibial plateau area (B=2.5, 95%CI 0.8-4.3), but negatively associated with lateral tibial cartilage volume (B=-4.9, 95%CI -8.4 to -1.5). The association of APMM and time from APMM with patellar cartilage defects was independent of tibial cartilage volume.

Conclusions: Partial medial meniscectomy is associated with adverse effects on articular cartilage and subchondral bone, which are associated with subsequent osteoarthritis, in both tibiofemoral and patellofemoral compartments.

The objective of this work is to evaluate differences in trabecular bone (TB) texture between sub... more The objective of this work is to evaluate differences in trabecular bone (TB) texture between subjects with and without tibiofemoral cartilage defects using a variance orientation transform (VOT) method. A case–control study was performed in subjects without radiographic knee OA (K&L grade<2) matched on sex, BMI, age, knee compartment and meniscectomy where cases (n=28) had cartilage defects (grade≥2) and controls (n=28) had no cartilage defects (grade<2). Cartilage defects were assessed from MRI using validated methods. The VOT was applied to TB regions selected on medial and lateral compartments in knee X-rays and fractal signatures (FS) in the horizontal ( ) and vertical ( ) directions, and along the roughest part of TB ( ) and texture aspect ratio signatures ( ), at different trabecular image sizes (0.30-0.70 mm) were calculated. Compared with controls, for cases were higher (P<0.011) at image sizes 0.30-0.40 mm and 0.45–0.55 mm in the medial compartment. In the lateral compartment, and for cases were higher (P<0.028) than those for controls at 0.30-0.40 mm and 0.45–0.55 mm, while was higher (P<0.02) at 0.30-0.40 mm. TB texture roughness was greater in subjects with cartilage defects than in subjects without, suggesting thinning and fenestration of TB occur early in OA and that the VOT identifies changes in TB in knees with early cartilage damage. No differences in (P>0.05) were found.

INTRODUCTION:: Prophylactic taping is commonly used to prevent ankle injuries during sports. Howe... more INTRODUCTION:: Prophylactic taping is commonly used to prevent ankle injuries during sports. However unnatural constraint of the ankle joint may increase the risk of injury to proximal joints such as the knee. The association between ankle taping and knee joint loading during open sporting tasks has not been quantified. This research aimed to measure changes in knee and ankle kinetics and kinematics during dynamic athletic activities undertaken with and without ankle taping

METHODS:: A kinematic and inverse dynamics model was used to determine ankle and knee joint motion and loading in 22 healthy male participants undertaking running and sidestepping tasks. Both tasks were randomized to planned and unplanned conditions, and undertaken with and without the use of ankle tape.

RESULTS:: At the knee, internal rotation moments (p=<0.001) and varus moments (p<0.05) were reduced for all tasks. Internal rotation impulse (p<0.001) was reduced for sidestepping tasks. Varus impulse during unplanned sidestepping maneuvers (p=0.04) was reduced with the use of ankle tape. However there was a trend toward increased valgus moments and impulse for planned sidestepping trials undertaken with ankle tape (p=0.056). Taping reduced the range of motion at the ankle in all three planes (p<0.05). Peak inversion (p<0.001) was reduced for running trials only. Average eversion and peak dorsiflexion moments were significantly reduced in sidestepping tasks by use of taping.

CONCLUSION:: By limiting motion at the ankle, taping increased mechanical stability at this joint. Ankle taping also provided protective benefits to the knee via reduced internal rotation moments and varus impulses during both planned and unplanned maneuvers. Medial collateral and anterior cruciate ligament injuries may, however, occur through increased valgus impulse during sidestepping undertaken with ankle tape.

Background: Common lower limb postures have been found when noncontact anterior cruciate ligament... more Background: Common lower limb postures have been found when noncontact anterior cruciate ligament (ACL) injuries occur during sidestep cutting tasks. These same postures have been linked to knee loadings known to stress the ACL.
Hypothesis: Whole body technique modification would reduce knee loading.

Study Design: Controlled laboratory study.

Methods: Experienced team sport athletes were recruited for whole body sidestep cutting technique modification. Before and
after a 6-week technique modification training, participants performed sidestep cutting tasks while ground-reaction force and motion data were collected. A kinematic and inverse dynamics model was used to calculate 3-dimensional knee loading during sidestep cutting.

Results: At initial foot contact, the participants placed their stance foot closer to the body’s midline and held their torso more upright, in line with the aims of the technique modification training. This was accompanied by significantly lower peak valgus moments in the weight acceptance phase of stance. Both postural changes were correlated with the change in peak valgus moment.

Conclusion: Whole body sidestep cutting technique modification resulted in reduced knee loading.

Clinical Relevance: Implementation of whole body technique modification may produce effective ACL injury prevention programs in sports involving sidestep cutting.

Medicine & Science …, Jan 1, 2007

Purpose: To identify the effect of modifying sidestep cutting technique on knee loads and predict... more Purpose: To identify the effect of modifying sidestep cutting technique on knee loads and predict what impact such change would have on the risk of noncontact anterior cruciate ligament injury.

Methods: A force platform and motion-analysis system were used to record ground-reaction forces and track the trajectories of markers on 15 healthy males performing sidestep cutting tasks using their normal technique and nine different imposed techniques. A kinematic and inverse dynamic model was used to calculate the three-dimensional knee postures and moments.

Results: The imposed techniques of foot wide and torso leaning in the opposite direction to the cut resulted in increased peak valgus moments experienced in weight acceptance. Higher peak internal rotation moments were found for the foot wide and torso rotation in the opposite direction to the cut techniques. The foot rotated in technique resulted in lower mean flexion/extension moments, whereas the foot wide condition resulted in higher mean flexion/extension moments. The flexed knee, torso rotated in the opposite direction to the cut and torso leaning in the same direction as the cut techniques had significantly more knee flexion at heel strike.

Conclusion: Sidestep cutting technique had a significant effect on loads experienced at the knee. The techniques that produced higher valgus and internal rotation moments at the knee, such as foot wide, torso leaning in the opposite direction to the cut and torso rotating in the opposite direction to the cut, may place an athlete at higher risk of injury because these knee loads have been shown to increase the strain on the anterior cruciate ligament. Training athletes to avoid such body positions may result in a reduced risk of noncontact anterior cruciate ligament injures.

Does Sidestepping Technique Modification Alter Muscle Co-Contraction At The Knee? Alasdair R Demp... more Does Sidestepping Technique Modification Alter Muscle Co-Contraction At The Knee?
Alasdair R Dempsey, Bruce C Elliott, David G Lloyd
School of Sport Science, Exercise and Health, The University of Western Australia, Crawley, Australia
Introduction: ACL injuries are severe occur frequently within sports. High knee valgus moments cause high ACL loads which can be reduced with technique modification. Co-contraction of the muscles crossing supports valgus moments during sidestepping. To thoroughly assess the efficiency of injury prevention programs both applied moments and muscular support need to be assessed.
Methods: Electromyography (EMG) data was collected from ten muscles crossing the knee during either a run, a sidestep, or a crossover cut under planned and unplanned conditions. Participants were tested prior and following six weeks of training. EMG was processed using a liner envelope and normalized to EMG occurring during planned runs. Flexion/Extension (FE) and Medial/Lateral (ML) ratios were calculated such that 1 represented pure Flexion/Medial activation, 0 equal activation and -1 Extension/Lateral activation. Total activation (TA) was also calculated. Mean co-contraction and TA were calculated for 50ms prior to foot strike (PC) and foot strike to the first trough in the vertical ground reaction force (WA). Eight linear mixed models were performed to identify differences for condition and time.
Results and Discussion: There were no observed differences during PC or TA in WA. There was no time effect for FE however unplanned tasks were more extensor dominated (-0.296) than planned sidesteps (-0.098). There was no main effects in ML however there was an interaction effect. Both tasks initially had perfect co-contraction (-0.16 Planned and 0.88 Unplanned) with planned tasks becoming medial dominated (0.133) and unplanned tasks becoming lateral dominated (-0.152).
The significant changes over time for ML during WA are negligible as values below 0.2 still represent similar levels of activation between muscle groups. With the only time changes being negligible, technique modification training during sidestep cutting is effective at reducing ACL loads as it reduced knee valgus moments while maintaining similar levels of co-contraction