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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
  1. Thomas J West1,2,
  2. Andrea M Bruder1,2,
  3. Kay M Crossley1,2,
  4. Adam G Culvenor1,2
  1. 1La Trobe Sport and Exercise Medicine Research Centre, School of Allied Health, Human Services and Sport, La Trobe University, Bundoora, Victoria, Australia
  2. 2Australian IOC Research Centre, La Trobe University, Bundoora, Victoria, Australia
  1. Correspondence to Dr Adam G Culvenor, La Trobe University, Melbourne, VIC 3086, Australia; a.culvenor{at}


Objective To investigate the prognostic capacity of individual hop tests, hop test batteries and other unilateral functional performance tests following anterior cruciate ligament (ACL) injury.

Design Systematic review with meta-analysis.

Data sources Six databases searched up to June 2021.

Eligibility criteria Studies reporting associations between unilateral lower-limb function (eg, hop tests) following ACL injury and future (≥3 months) knee-related outcomes.

Results Of 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).

Conclusion Very 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 number CRD42018092197.

  • Anterior Cruciate Ligament
  • Knee injuries
  • Knee
  • Rehabilitation
  • Physical Therapy Modalities

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  • Twitter @tsewmot, @AndreaBruder, @kaymcrossley, @agculvenor

  • Contributors TJW, AGC, AMB and KMC designed the study. TJW and AGC completed all searches, study selection (including inclusion and exclusion of abstracts). TJW and AGC completed all data extraction. TJW and AMB completed all risk of bias assessment. TJW and AGC and KMC planned the analyses, TJW completed the meta-analyses and all authors interpreted the data. TJW wrote the initial draft and all authors critically revised the manuscript for important intellectual content approved the final version of the manuscript.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.