Article Text

Evidence of ACL healing on MRI following ACL rupture treated with rehabilitation alone may be associated with better patient-reported outcomes: a secondary analysis from the KANON trial
  1. Stephanie Rose Filbay1,
  2. Frank W Roemer2,3,
  3. L Stefan Lohmander4,
  4. Aleksandra Turkiewicz5,
  5. Ewa M Roos6,
  6. Richard Frobell4,
  7. Martin Englund5
  1. 1Department of Physiotherapy, Faculty of Medicine Dentistry and Health Sciences, The University of Melbourne, Melbourne, Victoria, Australia
  2. 2Radiology, Universitatsklinikum Erlangen, Erlangen, Germany
  3. 3Radiology, Boston University School of Medicine, Boston, Massachusetts, USA
  4. 4Department of Clinical Sciences Lund, Orthopaedics, Lunds Universitet, Lund, Sweden
  5. 5Department of Clinical Sciences Lund, Orthopedics, Clinical Epidemiology Unit, Lund University, Lund, Sweden
  6. 6Department of Sports and Clinical Biomechanics, University of Southern Denmark, Odense, Syddanmark, Denmark
  1. Correspondence to Dr Stephanie Rose Filbay, Department of Physiotherapy, The University of Melbourne Faculty of Medicine Dentistry and Health Sciences, Melbourne, VIC 3010, Australia; stephanie.filbay{at}


Objectives Evaluate the natural course of anterior cruciate ligament (ACL) healing on MRI within 5 years of acute ACL rupture and compare 2-year and 5-year outcomes based on healing status and treatment group.

Methods Secondary analysis of 120 Knee Anterior Cruciate Ligament Nonsurgical vs Surgical Treatment (KANON) trial participants randomised to rehabilitation and optional delayed ACL reconstruction (ACLR) or early ACLR and rehabilitation. ACL continuity on MRI (Anterior Cruciate Ligament OsteoArthritis Score 0–2) was considered evidence of ACL healing. Outcomes included Knee Injury and Osteoarthritis Outcome Score (KOOS), KOOS patient acceptable symptomatic state (PASS) and treatment failure criteria. Linear mixed models were used to estimate adjusted mean differences (95% CIs) in patient-reported sport and recreational function (KOOS-Sport/Rec) and quality of life (KOOS-QOL) at 2 and 5 years, between participants with MRI evidence of ACL healing and those who had (1) no evidence of ACL healing, (2) delayed ACLR or (3) early ACLR.

Results MRI evidence of ACL healing at 2-year follow-up was observed in 16 of 54 (30%, 95% CI 19 to 43%) participants randomised to optional delayed ACLR. Excluding participants who had delayed ACLR, 16 of 30 (53%, 36–70%) participants managed with rehabilitation-alone displayed MRI evidence of ACL healing. Two-year outcomes were better in the healed ACL group (n=16) compared with the non-healed (n=14) (mean difference (95% CI) KOOS-Sport/Rec: 25.1 (8.6–41.5); KOOS-QOL: 27.5 (13.2–41.8)), delayed ACLR (n=24) (KOOS-Sport/Rec: 24.9 (10.2–39.6); KOOS-QOL: 18.1 (5.4–30.8)) and early ACLR (n=62) (KOOS-Sport/Rec: 17.4 (4.1–30.7); KOOS-QOL: 11.4 (0.0–22.9)) groups. Five-year KOOS-QOL was better in the healed versus non-healed group (25.3 (9.4–41.2)). Of participants with MRI evidence of ACL healing, 63–94% met the PASS criteria for each KOOS subscale, compared with 29–61% in the non-healed or reconstructed groups.

Conclusions MRI appearance of ACL healing after ACL rupture occurred in one in three adults randomised to initial rehabilitation and one in two who did not cross-over to delayed ACLR and was associated with favourable outcomes. The potential for spontaneous healing of the ACL to facilitate better clinical outcomes may be greater than previously considered.

Trial registration number ISRCTN84752559.

  • anterior cruciate ligament
  • rehabilitation
  • Magnetic Resonance Imaging
  • osteoarthritis
  • quality of life

Data availability statement

Data are available upon reasonable request.

This is an open access article distributed in accordance with the Creative Commons Attribution 4.0 Unported (CC BY 4.0) license, which permits others to copy, redistribute, remix, transform and build upon this work for any purpose, provided the original work is properly cited, a link to the licence is given, and indication of whether changes were made. See:

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.

Supplementary materials


  • RF and ME are joint senior authors.

  • Twitter @stephfilbay, @ewa_roos

  • Correction notice This article has been corrected since it was first published. The open access licence has been updated to CC BY.

  • Contributors All authors conceived and designed this analysis and participated in interpretation of findings. AT performed the statistical analysis. FWR analysed the MRI data. SRF drafted the first version of the manuscript. All authors contributed in revising the manuscript and gave their final approval of the submitted version. SF accepts full responsibility for the overall content and study conduct, AT is responsible for the statistical analysis.

  • Funding The KANON study received funding from the Swedish Research Council (RBF, LSL, EMR), Medical Faculty of Lund University (RBF, LSL, EMR), Region Skåne (LSL, RBF, EMR), Thelma Zoegas Fund (RBF), Stig & Ragna Gorthon Research Foundation (RBF), Swedish National Centre for Research in Sports (LSL, RBF), Crafoord Foundation (RBF), Tore Nilsson Research Fund (RBF) and Pfizer Global Research (LSL). SRF is funded by a National Health and Medical Research Council (NHMRC) Investigator Grant (number 1194428).

  • Competing interests EMR is deputy editor of Osteoarthritis and Cartilage, the developer of Knee injury and Osteoarthritis Outcome Score and co-founder of the Good Life with Osteoarthritis in Denmark (GLA:D) initiative to implement clinical guidelines in primary care; FWR is a shareholder of Boston Imaging Core Lab, and Consultant to Calibr and Grünenthal outside the submitted work.

  • Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

  • 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.