Abstract
BACKGROUND: Dynamic knee valgus (DKV) is widely considered a risk factor for injuries, despite contradictory research. Consequently, athletic performance and injury rehabilitation cueing has primarily focused on keeping the "knees out". PURPOSE: The purpose of this study was to assess jump performance measures and anatomical contributions. STUDY DESIGN: Cross-Sectional Study. METHODS: Jump height, ground contact time, reactive strength index, and DKV was collected with the MyJump2 and Coach My Video apps. Static anatomical measurements were collected. Subjects completed nine jumps with each leg using the same set-up; performing three single leg six-inch depth jumps with their natural form, three depth jumps with external cuing towards increased DKV, and three depth jumps with cuing towards no DKV. ANOVA was used to compare jump data. Pearson Correlation Coefficients were used to assess relationships between DKV and anatomical measurements, jump height, ground contact time, and reactive strength index. Intraclass correlation coefficient (ICC) was used to assess inter-rater reliability of MyJump2 and Coach My Video measurements. RESULTS: 50 subjects (35 included) participated in this study. With a cued DKV jump, ground contact time had a moderate positive correlation with DKV measurements (r=.49, p<0.01), however, this was not the case with subjects' natural jump and cued no DKV alignment jumps. Static anatomical measurements of static knee valgus and Q-angle had a weak positive correlation with DKV measurements for subjects' natural jumps (r=.37, p<0.01 and r=.34, p=0.04, respectively). When DKV measurements were normalized to an anatomical measurement, no correlations existed with any of the performance measurements. There was very strong inter-rater reliability (ICC=.96-.99) of all the measurements. CONCLUSION: Bony anatomical alignment should be considered alongside kinematics, as normalization controlled for the differences in DKV. Future research should normalize DKV measurements by bony anatomy when addressing DKV and jump performance. LEVEL OF EVIDENCE: 2c.