Knee valgus during drop jumps in National Collegiate Athletic Association Division I female athletes: the effect of a medial post

BACKGROUND: Female athletes land from a jump with greater knee valgus and ankle pronation/eversion. Excessive valgus and pronation have been linked to risk of anterior cruciate ligament injury. A medially posted orthosis decreases component motions of knee valgus such as foot pronation/eversion and tibial internal rotation.

HYPOTHESIS: We hypothesized a medial post would decrease knee valgus and ankle pronation/eversion during drop-jump landings in NCAA-I female athletes.

STUDY DESIGN: Controlled laboratory study.

METHODS: Knee and ankle 3-dimensional kinematics were measured using high-speed motion capture in 10 National Collegiate Athletic Association Division I female athletes during a drop-jump landing with and without a medial post. Analysis of variance was used to determine differences in posting condition, t tests were used to determine dominant-nondominant differences, and the Pearson correlation coefficient was used to determine relationships between variables.

RESULTS: Significant differences were found for all measures in the posted condition. A medial post decreased knee valgus at initial contact (1.24 degrees , P < .01) and maximum angle (1.21 degrees , P < .01). The post also decreased ankle pronation/eversion at initial contact (0.77 degrees , P < .01) and maximum angle (0.95 degrees , P = .039).

CONCLUSION: The authors have demonstrated a significant decrease in knee valgus and ankle pronation/eversion during a drop jump with a medial post placed in the athletes' shoes.

CLINICAL RELEVANCE: A medial post may be a potential means to decrease risk of anterior cruciate ligament injury.