(21) Knee Mechanics During Cutting Maneuvers: Gender Differences in Noncontact Acl Injury Rates (original) (raw)

2004, Clinical Journal of Sport Medicine

Introduction: It is well known that females have a higher incidence of stress fractures (SFs) than males, especially during military service; however, the reasons are not completely clear. In this study, we followed up a group of female recruits in order to define the risk factors for SF and other injuries. Participants and Design: Eighty-three female infantry recruits were prospectively followed up during a 4-month course of basic training. Participants filled out a questionnaire concerning health status, previous physical activity, and menstrual history. A detailed orthopedic examination was performed, and footprints were taken. During the course, follow-up of injuries was done by interview twice a month, and all clinic visits were documented. Results: Of the total 83 recruits, 15 suffered low back pain (LBP), 21 had anterior knee pain (AKP), 27 had an ankle sprain (AS), and 16 were diagnosed with SF, with a total of 33 SF and 31 AS. Eleven complained of foot pain and 22 of shin pain. The recruits suffering SF had nearly double the number of AS, 3 times the AKP, and more than 3 times the number of complaints of foot pain, but no more LBP than those not suffering a SF. Of the SFs, 10 were grade 2 and 6 were grade 3. Twenty were considered dangerous according to location. Thirty-nine percent were located in the tibia and 15% in the femur. SF was not affected by height, weight, BMI, or the arch of the foot. A tendency for a higher occurrence of SF was found in participants with irregular menstruation (P = 0.17; and for dangerous SF, P = 0.05) and an older age of menarche (P = 0.14). A mild tendency for less dangerous stress fracture was shown in those with a higher use of milk products (P = 0.25), and those taking birth control pills showed a mild tendency for stress fracture reduction (P = 0.24). Scoliosis seemed to cause dangerous stress fracture (P = 0.06), and a valgus heel showed a possible mild tendency for the same (right foot, P = 0.09; left foot, P = 0.22), as more so did ankle instability (right foot, P = 0.03; left foot, P = 0.15). Conclusions: In this study of female infantry recruits, 20% to 30% suffered SF, LBP, AKP, and acute AS. Amenorrhea and late menarche and possibly irregular menstruation, unstable ankles, and heel valgus seem to be related to SF in female infantry recruits, especially the dangerous fractures occurring in the shaft of the long bones.