Purpose Elastic knee sleeves are often worn following anterior cruciate ligament reconstruction but mechanisms underlying observed changes in movement patterns are still unclear. The aim of this study was to determine the immediate and 6-week effects of wearing a knee sleeve on ground reaction forces (GRF) and knee joint power during a step-down hop task. Methods Using a cross-over design, we estimated GRF and knee kinematics and kinetics during a step-down hop for 30 participants (age 26.1 [SD 6.7] years, 14 women) following ACL reconstruction (median 16 months post-surgery) with and without wearing a knee sleeve. In a subsequent randomised clinical trial, participants in the ‘Sleeve Group’ (n=9) then wore the sleeve for 6 weeks at least 1 hour daily, while a ‘Control Group’ (n=9) did not wear the sleeve. Statistical parametric mapping (SPM) was used to compare (1) GRF trajectories in the three planes as well as knee joint power between three conditions at baseline (uninjured side, unsleeved injured and sleeved injured side); (2) within-participant changes for GRF and knee joint power trajectories from baseline to follow-up between groups. We also compared discrete peak GRFs and power, rate of (vertical) force development, and mean knee joint power in the first 5% of stance phase. Results GRF did not differ for the (unsleeved) injured compared to the uninjured sides based on SPM analysis. Discrete variables showed lower peak anterior (propulsive) GRF for the injured side, and lower peak eccentric and concentric power, and mean power in the first 5% of stance.  When wearing the sleeve on the injured side, mean power in the first 5% of stance increased significantly [mean difference (95% CIs) 1.3 (0.6, 2.0) N/BW*ht] from a concentric to an eccentric power when wearing the knee sleeve. After six weeks, the direction of change for vertical GRF differed between the groups: while the Control Group had slightly decreased forces, the Sleeve Group presented increased forces. Conclusions Increased knee power in the first 5% of landing when wearing the knee sleeve, combined with greater knee flexion, may indicate a protective response for ACL ruptures, most commonly occurring during that early phase of landing. The directional change of increased vertical GRF for the Sleeve group, combined with shorter stance duration at follow-up, may indicate enhanced performance when being prescribed such sleeve.

The authors have declared that no competing interests exist.

The trial was prospectively registered with the Australia New Zealand Clinical Trials Registry No: ACTRN12618001083280, 1st October 2018

https://anzctr.org.au/Trial/Registration/TrialReview.aspx?id=375347&isClinicalTrial=False

Funding and material (knee sleeves) were provided by Bauerfeind AG (Triebeser Straße, 07937 Zeulenroda-Triebes, Germany. The grant holders are Gisela Sole, Niels Hammer, Todd Pataky, Peter Lamb. The Funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Ethics approval was granted by the Health & Disability Ethics Committee, New Zealand, Reference 18/CEN/93, dated 5th June 2018, amended on 27th August 2019 and 4th October 2019.

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable.

Yes