Objectives To investigate lower extremity muscle strength as risk factor for an acute ankle injury in youth athletes.

Design Cohort study.

Setting Basketball and floorball clubs.

Participants 188 youth (≤21) male and 174 female athletes.

Main outcome measures 1RM leg press, maximal concentric isokinetic quadriceps and hamstrings as well as maximal isometric hip abductor strength were measured and athletes were followed for an acute ankle injury up to three years. Cox regression models were used in statistical analyses.

Results In males, greater 1RM leg press and maximal quadriceps strength increased the risk of any type of acute ankle injury (Hazard ratio [HR] for 1 SD increase, 1.63 [95% CI, 1.12–2.39] and 1.43 [95% CI, 1.01–2.01], respectively). In females, greater 1RM leg press and difference between legs in hip abduction strength increased the risk of acute non-contact ankle injury (HR for 1 SD increase, 1.44 [95% CI, 1.03–2.02] and 1.44 [95% CI, 1.03–2.00], respectively). However, ROC curve analyses showed AUC:s of 0.57–0.64 indicating “fail” to “poor” combined sensitivity and specifity of these tests.

Conclusion Greater strength in both sexes along with asymmetry in hip abductor strength in females increased the risk of acute ankle injury.