Residual deficits in reactive strength indicate incomplete restoration of athletic qualities following anterior cruciate ligament reconstruction in professional soccer players

Context: Deficits in plyometric abilities are common following anterior cruciate ligament reconstruction (ACLR). Vertical rebound tasks may provide a targeted evaluation of knee function.
Objective: Examine the utility of a vertical hop test to assess function following ACLR and establish factors associated with performance.
Design: Cross-sectional
Setting: Rehabilitation
Participants: Soccer players with a history of ACLR (N = 73) and matched controls (N = 195)
Main outcome measures: 10 second vertical hop test including measures of jump height, reactive strength index (RSI) and asymmetry. We also examined possible predictors of hop performance including single leg vertical drop jump (SLDVJ), isokinetic knee extension strength, and the international knee documentation committee questionnaire.
Results: Significant between-limb differences were identified for the ACLR group only and asymmetry scores increased in those with a history of ACLR (P < 0.001) compared to controls. SLDVJ RSI and knee extension torque were significant predictors of 10 second hop
height (R2 = 20.1%) and RSI (R2 = 47.1%).
Conclusions: Vertical hop deficits are present following ACLR even after completing a comprehensive rehabilitation program. This may be due to reduced knee extension and reactive strength. Vertical hop tests warrant inclusion as part of return to sport test battery.