Neuromuscular Control and Valgus Loading of the Knee Predict ACL Injury Risk in Female Athletes

2001

PURPOSE: Females suffer ACL injury at a 4 to 6-fold greater rate than males. Geometric growth in participation, coupled with the higher injury rate, has lead to a large increase in the number of ACL injuries in female athletes. The hypotheses tested in this study were that pre-screened females that went on to ACL injury would demonstrate decreased neuromuscular control and increased joint loading, which would predict ACL injury risk. METHODS: 205 female athletes in high-risk sports were prospectively measured for neuromuscular control using 3-D kinematics (joint angles) and joint loads using kinetics (joint moments) during jump landing. ANOVA, linear and logistic regression compared groups and identified predictors of risk from ACLinjured athletes. RESULTS: The 9 of 205 athletes that had confirmed ACL rupture demonstrated increased valgus and external knee abduction moment (KABM). Knee abduction angle (KABA) at landing was 8° greater at initial contact (IC) and maximum excursion. Knee flexion angle (KFA) was not different at IC, but 10° lower at peak excursion in ACL-injured than uninjured athletes (p<0.05). ACL-injured had a 2.5- times greater KABM (p<0.001) and 20% higher ground reaction force (GRF, p<0.05), while stance time was 16% shorter (p<0.001). KABM and KABA correlated to GRF (R = 0.74 and R = 0.67, p< 0.05) and hip adduction moment (R = 0.69, p< 0.05) in ACL-injured subjects. KFA did not correlate to GRF (p = 0.36). KABM predicted ACL injury status with 73% specificity and 78% sensitivity and combined valgus measures showed a predictive r2 value of 0.88. CONCLUSIONS: Decreased control (valgus) and high loading (abduction moment) predict ACL injury risk in females. The methods developed in this report may be used to monitor altered neuromuscular control and increased valgus loading of the knee joint in female athletes. These measures of neuromuscular imbalance, neuromuscular control and joint loading may be used to direct potentially high-risk athletes to more effective, targeted interventions.

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