ACL Injuries: Do You Actually Need Surgery?

When I tore my ACL, nobody gave me a choice. 

For years the knee-jerk reaction to an ACL injury was “You’ll need surgery”

The thinking was that an ACL cannot heal and the only way to regain stability to return to sport was to have a reconstruction. 

But research is showing that this may not be the case. 

What Does The Research Actually Say?

Several high quality trials and cohort studies have changed how we think about ACL management.

The KANON trial found no meaningful difference in outcomes between early surgery and rehab with optional delayed reconstruction at 2 and 5 years - surgery was unnecessary in at least half of patients.

The COMPARE trial supported this - early surgery scored marginally better at 2 years, but the difference wasn't clinically meaningful, and again 50% of the rehab group never needed surgery.

A large Norwegian nationwide cohort found that two-thirds remained non-operative at 2 years. When people did opt for surgery, it was driven by ongoing instability - not meniscal damage as is often feared.

Three studies. Similar conclusions.

Somewhere between 50-67% managed their injury successfully without surgery - suggesting that for many people, reconstruction is not inevitable.

Across all of this research, one theme is consistent: a significant proportion of ACL-injured patients do well without surgery.

So it is worth trialling rehab, finding out how the knee is responding and making an informed decision from there.

And can the ACL actually heal?

In short, Yes. 

A secondary analysis from the KANON trial showed that injured ACLs showed signs of healing on MRI as early as 3 months after injury. 

At 2 years, 53% of non-surgical patients showed ACL healing on MRI - roughly 1 in 3 participants overall. The most striking finding: those who showed healing had better 2-year outcomes than those who didn't heal or those who had surgery.

This doesn't mean everyone should avoid surgery. 

But it does mean the old assumption that an ACL can never heal is wrong.

So the real question isn't "do I need surgery?"

It's: “How does my knee respond to rehab?”

The first phase after an ACL injury is about calming the knee down - reducing swelling, restoring movement, regaining quad strength, and rebuilding confidence. 

Even if surgery is eventually needed, this phase is never wasted time. People who complete strong pre-operative rehab consistently have better outcomes afterwards. They go into surgery with a stronger, calmer, more functional knee.

Who typically does well without surgery?

In my experience it comes down to five things: 

• Physical Performance

• Symptoms

• Goals

• Sport

• Lifestyle 

For example,

A 21-year-old female rugby player who tore her ACL sidestepping, wants to return to rugby, has a low training age, and is experiencing regular instability despite rehab — she is more likely to need surgery.

A 50-year-old runner who tore his ACL on his first ski trip, trains regularly, has responded well to the first month of rehab, has no interest in skiing again, and just wants to get back to his 10ks — he may well do fine without it.

The rehab in the early stages is almost identical either way. The difference is in where that rehab leads.

The 7Rs of ACL Rehabilitation

Whether you go down the surgical or non-surgical route, structured rehabilitation follows the same pathway. This is my 7Rs framework that takes athletes from the acute injury phase all the way back to full performance.

As you can see it is pretty much the same for non-operative management as it is for if you have surgery. You basically go along the framework, constantly testing, and if it’s going well and you can cope - you just keep going.

If you can’t cope at any stage and you opt for surgery, that effectively becomes your prehab. And you go into an almost identical framework. 

What should you do? 

Well, if you've just injured your ACL or you're months into a rehab, the best first step is a proper assessment.

This assessment is a bit like a Google Maps - we need to know where you currently (how your knee is functioning, range, strength, power), your destination, where you need to get to (your goals, sports and activities that matter to you) and if there are any road blocks along the way (previous injuries, age, baseline physical preparedness).

Not sure where your ACL rehab should go next? Drop me a message and we can work it out together

Contact Me Now 💻

Will Harris

BSc. Physiotherapy CSP 100101

HCPC PH110158

References:

1. Frobell R, et al. A randomized trial of treatment for acute anterior cruciate ligament tears. New England Journal of Medicine. 2010;363:331–42.

2. Frobell R, et al. Treatment for acute anterior cruciate ligament tear: five year outcome of randomised trial. BMJ. 2013;346.

3. Filbay S, et al. 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. British Journal of Sports Medicine. 2023;57:91–98.

4. Reijman M, et al. Early surgical reconstruction versus rehabilitation with elective delayed reconstruction for patients with anterior cruciate ligament rupture: COMPARE randomised controlled trial. BMJ. 2021;372:n375.

5. Kooy C, et al. Non-operative treatment of anterior cruciate ligament injuries: two-thirds avoid surgery at 2-year follow-up in a nationwide cohort. British Journal of Sports Medicine. 2025;59:1743–1751.

6. Weiler R, et al. Non-operative management of a complete anterior cruciate ligament injury in an elite professional footballer. BMJ Case Reports. 2015.