Unilateral tests of lower-limb function as prognostic indicators of future knee-related outcomes following anterior cruciate ligament injury: a systematic review and meta-analysis of 13 150 adolescents and adults

ObjectiveTo investigate the prognostic capacity of individual hop tests, hop test batteries and other unilateral functional performance tests following anterior cruciate ligament (ACL) injury.DesignSystematic review with meta-analysis.Data sourcesSix databases searched up to June 2021.Eligibility criteriaStudies reporting associations between unilateral lower-limb function (eg, hop tests) following ACL injury and future (≥3 months) knee-related outcomes.ResultsOf 42 included studies (13 150 participants), all assessed the single-forward hop test and 32 assessed a repeated-forward hop test (crossover hop, triple hop, 6m-timed hop), mostly within a year after ACL injury/reconstruction. Results of meta-analyses indicated that higher single-forward and repeated-forward hop limb symmetry were associated with higher odds of return-to-sport 1–3 years post-ACL reconstruction (OR 2.15; 95% CI 1.30 to 3.54; OR 2.11; 95% CI 1.23 to 3.60, respectively). Higher single-forward and repeated-forward hop limb symmetry was associated with better self-reported symptoms and function 1–37 years after ACL injury (OR 2.51; 95% CI 1.62 to 3.88; OR 4.28; 95% CI 1.65 to 11.08, respectively). Higher limb symmetry on a repeated-forward hop does not appear to be associated with higher odds of successful rehabilitation without ACL reconstruction (OR 1.51; 95% CI 0.94 to 2.44). Achieving ≥90% limb symmetry on the single-forward hop was associated with reduced odds of knee osteoarthritis 5–37 years after ACL injury (OR 0.46; 95% CI 0.23 to 0.94).ConclusionVery low certainty evidence suggests single-forward and repeated-forward hop tests are prognostic indicators for important knee-related outcomes in individuals after ACL injury and may help stratify individuals at risk of poor outcomes to target rehabilitation interventions.PROSPERO registration numberCRD42018092197.