Comparison of surgical or non-surgical management for non-acute anterior cruciate ligament injury: the ACL SNNAP RCT.

When someone tears their anterior cruciate ligament but doesn't have surgery right away, the question of what to do next has long been unclear. Should they go straight to reconstructive surgery, or try physiotherapy-based rehabilitation first and only operate if the knee remains unstable? This trial randomised patients with long-standing ACL injury and instability symptoms to one of these two strategies and followed them for eighteen months, measuring knee function, activity levels, satisfaction, and costs. Both groups improved over time, but those assigned to surgery first ended up with better knee function scores, higher satisfaction, and more quality-adjusted life, though at greater cost to the health service. Notably, many patients initially assigned to rehabilitation still ended up having surgery, and adherence to physiotherapy was described as patchy, which complicates interpretation of how rehabilitation alone performed.

The findings suggest surgical reconstruction without delay may serve later-presenting patients better, though rehabilitation still produced meaningful within-group improvement for many.

If you've had an ACL injury that's been going on for a while and your knee feels unstable, doctors have not had strong evidence about whether it's better to get surgery straight away or try physiotherapy first and see how things go. This trial followed 316 people from hospitals across the UK, splitting them into two groups: one had knee reconstruction surgery without delay, and the other did structured physiotherapy first, having surgery later only if their knee stayed unstable. People in both groups got better over the eighteen months of the study.

But those who had surgery straight away reported somewhat better knee function, higher satisfaction with their treatment, and slightly more improvement in overall quality of life, although this came with higher costs to the health service. Interestingly, some people assigned to rehabilitation still chose surgery later, and not everyone stuck closely to their physiotherapy plan, which makes it harder to know exactly how well rehabilitation alone would have worked if followed more strictly.

Both approaches are options that people can discuss with their own care team.

This is a summary of research, not medical advice. Talk to your own healthcare provider about anything affecting your care.

This pragmatic, multicentre randomised controlled trial (n=316, 29 UK NHS orthopaedic units) compared upfront surgical reconstruction with an initial rehabilitation strategy (surgery reserved for continued instability) in patients with non-acute, symptomatic ACL injury. Primary outcome was Knee Injury and Osteoarthritis Outcome Score 4 (KOOS4) at 18 months, with 78% follow-up (n=248).

Adjusted mean KOOS4 was 73.0 in the surgical arm versus 64.6 in the rehabilitation arm, a mean difference of 7.9 (95% CI 2.5 to 13.2, p=0.005) favouring surgery, supported by per-protocol analyses. Crossover was substantial: 41% of the rehabilitation group underwent reconstruction within 18 months, while only 72% of the surgical arm actually received surgery, and physiotherapy adherence was described as patchy, both of which limit clean separation between strategies and should temper causal attribution of benefit purely to the allocated pathway. Satisfaction favoured surgery (82.9% vs 68.1%), with no between-group difference in complications or clinical events.

Health economic analysis found a modest, non-significant quality-adjusted life-year gain (0.052, p=0.177) but significantly higher costs (£1107, p<0.001) with surgery, yielding an incremental cost-effectiveness ratio of £19,346 per quality-adjusted life-year, judged cost-effective at standard UK thresholds. Confirmatory trials addressing fidelity and adherence are warranted.