Generalised joint hypermobility and excess knee hyperextension are associated with an increased risk for second ACL injury, but not primary ACL injury, in female football players: A 5‐year follow‐up

PURPOSE: This study aimed to investigate the association between generalised joint hypermobility, knee hyperextension, knee laxity, and static standing alignment with the risk of anterior cruciate ligament (ACL) injury in a cohort of female football players with an ACL-reconstructed (ACLR) knee and in knee-healthy controls. METHODS: We prospectively followed 117 female football players with ACLR (age, mean ± standard deviation, 20 ± 2 years; average 19 ± 9 months after ACLR) and 119 knee-healthy players (age, 19 ± 3 years) for 5 years. At baseline, all players were assessed for generalised joint hypermobility (Beighton score), knee extension range of motion, knee laxity (KT-1000, Lachman and pivot shift tests), and static standing alignment (visual assessment graded as varus, valgus or neutral). Log-binomial regression with risk ratios (RRs) and 95% confidence intervals (CIs) for new ACL injury were calculated. Point biserial and Spearman's rank correlations were used for correlation analysis of baseline anatomical variables. RESULTS: During the 5-year follow-up, 43 ACLR players sustained a second ACL injury (30 re-ruptures and 13 contralateral ruptures) and 11 knee-healthy players had an index ACL injury. ACLR players with Beighton score ≥5 (RR, 1.67; 95% CI, 1.04-2.70; p = 0.035) and knee hyperextension >5° in the non-ACL-reconstructed knee (RR, 1.67; 95% CI, 1.02-2.73; p = 0.042) had higher risk of a second ACL injury; knee laxity and static standing alignment were not associated with a second ACL injury (n.s.). No significant associations were seen between baseline variables and index ACL injury in knee-healthy players (n.s.). There was moderate correlation between KT-1000 and the Lachman test (r = 0.594-0.673), and negligible to moderate correlations between other baseline variables. CONCLUSIONS: Generalised joint hypermobility and knee hyperextension were associated with an increased risk of second ACL injury in female football players with ACLR. Screening for generalised joint hypermobility and knee hyperextension may inform prevention strategies for female football players after ACL injury. LEVEL OF EVIDENCE: Level I.