Athletes Continue to Show Functional Performance Deficits at Return to Sport After Anterior Cruciate Ligament Reconstruction: A Systematic Review

Purpose To systematically review the existing literature on the functional performance of athletes at the time of return-to-sport (RTS) clearance following ACL-reconstruction (ACLR). Methods A systematic literature search was performed in MEDLINE, EMBASE, Scopus, and Web of Science. Inclusion criteria were original research report, a study population of athletes who had undergone ACLR, and had undergone objective functional testing immediately following clearance to RTS. Functional testing was stratified by hop tests, strength tests, kinetic assessment, and kinematic assessment, and were extracted from each study using a standardized template. Results Of the 937 unique studies identified, 46 studies met inclusion criteria. The average time between ACLR and functional testing was 7.9 months among included studies. Ten of 17 studies found patients to have an average quadriceps strength (QS) limb symmetry index (LSI) of less than 90%. However, only two out of 12 studies found the average hop test LSI to be less than 90%. Kinematics included reduced knee flexion angle and increased trunk flexion upon landing in ACLR patients compared to matched controls. In evaluating kinetics, ACLR patients also demonstrated reduced peak vertical ground reaction force (vGFR), lower peak knee extension and knee flexion moments, and altered energy absorption contribution compared to matched controls. Conclusions This systematic review suggests that athletes demonstrate functional deficits at the time of return to sports at an average of 7.9 months following ACL reconstruction. Traditional functional testing, such as strength and hop tests, are not able to accurately identify patients who continue to demonstrate deficits. The most common biomechanical deficits that persist after RTS clearance include diminished peak knee extension moment, decreased knee flexion angle, increased trunk flexion angle, reduced vertical ground reaction force, and increased hamstrings central activation ratio during various functional gait and landing tasks.