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Comparison of the clinical and cost effectiveness of two management strategies for non-acute Anterior Cruciate Ligament (ACL) injury: rehabilitation versus surgical reconstruction


Rupture of the Anterior Cruciate Ligament (ACL) is common but the resulting disability can be variable.  Some patients recover and cope fine without their ACL whilst others do not and continue to have episodes of knee instability/giving way affecting day to day activities, work and recreation.  It is often thought that these patients require surgery (ACL reconstruction) to stabilise the knee.  In the NHS it is estimated at least 14,000 primary ACL reconstructions are performed each year.

The variability, i.e. the effect of the injury being neither consistent nor predictable, means that clinical management varies from surgeon to surgeon and from hospital to hospital.  Some surgeons feel that patients should always undergo surgery (ACL reconstruction), and as soon as possible after being diagnosed. The rationale is that by not surgically stabilising an unstable knee, the knee might continue to buckle and give way which potentially causes further internal damage (of the cartilage) and can affect long term outcome.  Conversely some surgeons feel that a period of rehabilitation (exercises) should always be prescribed as it may be possible to avoid an operation altogether. 

Overall, the picture of management for the non-acute ACL deficient knee is confusing with limited and conflicting evidence for efficacy.  In addition, the costs to the health service are not insubstantial.  The benefits for either management approach are uncertain and therefore a new study is required to discover the best treatment option.

Study Design

We propose to carry out a randomised controlled trial with the following aim;

To determine, in patients with non-acute Anterior Cruciate Ligament Deficiency (ACLD), whether non-surgical treatment (with the option for later ACL reconstruction if required) is more effective than surgical ACL reconstruction (as measured by the Knee Injury and Osteoarthritis Outcome Score [KOOS4] at 18 months from randomisation).

Multi-centre superiority randomised controlled trial, parallel group two arm design with 1:1 allocation ratio.

  • Sample Size: 320 patients recruited from approx. 20 NHS orthopaedic units (with defined experience/volume).
  • Population: Patients with a non-acute unilateral symptomatic (unstable) ACL deficient knee.
    • Complete ACL tear confirmed by clinical assessment and/or MRI scan.
  • Interventions: Non-surgical management (rehabilitation) or surgical management (reconstruction).
  • Outcome: Knee Injury and Osteoarthritis Outcome Score (KOOS) at 18 months.


View the NIHR page here!


Trial Publications

The study protocol can be found here.

The Lancet paper can be found here



Old ACL Injury: Go Straight to OR, Skip Preop Rehab? | Orthopedics This Week (

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Selected publications

Related research themes