Hip and ankle strength and range of motion in female soccer players with dynamic knee valgus

BACKGROUND: Dynamic knee valgus (DKV) is a known risk factor for acute and chronic knee injuries and is more frequently diagnosed in females. A real-time single-leg squat test (SLST) could screen for DKV to prevent injuries. OBJECTIVE: To compare the differences in lower extremity strength and range of motion (ROM) in female soccer athletes with and without DKV during an SLST. METHODS: Eighteen subjects with DKV (DKV group) and 18 subjects without DKV (control group) during a single-leg squat were included. Hip strength (flexion, extension, abduction, adduction, internal rotation, and external rotation) was measured with a hand-held dynamometer. Hip ROM (internal and external rotation), and ankle ROM (dorsiflexion with the knee flexed and extended) were measured. Independent t-test was used to compare the averages of the groups. RESULTS: There were significant differences in hip abduction to adduction strength ratio (DKV: 1.48 +/- 0.3, control: 1.22 +/- 0.26, p < 0.01) and ankle dorsiflexion with knee flexed (DKV: 17.22 +/- 6.82, control: 21.22 +/- 4.55, p < 0.05) and extended (DKV: 10.14 +/- 4.23, control: 14.75 +/- 3.40, p < 0.001) between the groups. CONCLUSION: The hip abduction to adduction strength ratio and gastrocnemius and soleus flexibility may be associated factors in dynamic knee valgus and therefore should be assessed and treated, if indicated, as a possible preventive measure in female athletes with this variation.