Is Knee Separation During a Drop Jump Associated With XXXX in Adolescent Female Soccer Players?

@entity1 @entity3331 @entity130
BACKGROUND: @entity3331 are common in older adolescent and adult female soccer players, and abnormal valgus knee appearance characterized by low normalized knee separation (NKS) is a proposed @entity130 factor. What constitutes normal NKS in younger adolescents and whether low NKS is an @entity130 factor are unknown. PURPOSE: To determine the normal range of NKS using a drop-jump test in female perimenarchal youth soccer players and whether low NKS contributes to lower @entity130 or @entity3331 . STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: From 2008 to 2012, a total of 351 female elite youth soccer players (age range, 11-14 years) were followed for 1 season, with complete follow-up on 92.3% of players. Baseline drop-jump testing was performed preseason. Lower @entity130 during the season were identified using a validated, Internet-based injury surveillance system with weekly email reporting. Normalized knee separation at prelanding, landing, and takeoff was categorized 2 ways: as  <=10th percentile (most extreme valgus appearance) compared with >10th percentile and as a continuous measure of 1 SD. Poisson regression modeling with adjustment for clustering by team estimated the relative risk (RR) and 95% confidence interval (CI) of the association between the NKS and the risk of lower extremity and @entity3331 , stratified by menarche. RESULTS: Of the study @entity1 , 134 players experienced 173 lower @entity130 , with 43 (24.9%) @entity3331 . For postmenarchal players (n = 210), those with NKS  <=10th percentile were at 92% increased risk of @entity130 (RR, 1.92; 95% CI, 1.17-3.15) and a 3.62-fold increased risk of @entity3331 (RR, 3.62; 95% CI, 1.18-11.09) compared with NKS >10th percentile at prelanding and landing, respectively. Among postmenarchal players, there was an 80% increased risk of @entity3331 (RR, 1.80; 95% CI, 1.01-3.23) with a decrease of 1 SD in landing NKS and a 66% increased risk of @entity3331 (RR, 1.66; 95% CI, 1.04-2.64) with a decrease of 1 SD in takeoff NKS. Among premenarchal players (n = 141), there was no statistically significant association between the NKS at prelanding, landing, and takeoff and the risk of lower extremity or @entity3331 . CONCLUSION: Low NKS was associated with increased risk of lower extremity and @entity3331 only among postmenarchal players.
