Do I Need ACL Surgery? What the Evidence Says | GCKG
Do I Need ACL Surgery? What the Evidence Says About Rehabilitation Alone
Dr Adam Walker (PhD) — Director and Head of Rehabilitation, Gold Coast Knee Group
If you have torn your ACL in Australia, the working assumption in almost every room you walk into is that you are having surgery.
Around 90% of Australians who injure their ACL go on to a reconstruction. We do more of them, per head, than almost anywhere in the world.
So it is a slightly uncomfortable question to raise, but it is a fair one: does everyone actually need it?
Let me be clear about where I stand before we go any further. Plenty of people need an ACL reconstruction to get a stable, functional knee back, and I have excellent relationships with some of the best knee surgeons on the Gold Coast whose work I value enormously. This is not an argument against surgery.
It is an argument for making the decision properly — because there is a second option that a lot of people are never offered, and the research behind it is better than most people expect.
What “rehabilitation alone” actually means
It means treating the injury with a structured, progressive rehabilitation program rather than an operation, while keeping surgery available as an option if you need it later.
This is not new and it is not fringe. It has been happening for decades, and in a number of Scandinavian countries — which keep the best ACL injury registries in the world — it is standard practice to wait three months before reconstructing an ACL at all.
It is one of three options after an ACL injury. The others are the Cross Bracing Protocol, which aims to help the ligament heal, and early surgical reconstruction. There is also a genuinely excellent independent decision aid built by researchers at the University of Melbourne at aclinjurytreatment.com.
Is it safe to not have ACL surgery?
This is usually the real worry underneath everything else, so let us deal with it first.
Most people have been told, in one form or another, that leaving an ACL untreated means arthritis later and more damage in the meantime. It is a reasonable thing to be afraid of, and it is worth knowing what the evidence actually shows.
Arthritis risk
A systematic review with at least ten years of follow-up found that whether or not someone had surgery did not change their risk of developing knee osteoarthritis4. There is a considerable body of research pointing the same way. Surgery does not appear to protect the joint from arthritis.
Further damage to the knee
The same review found the risk of further meniscus tears and cartilage injuries was also similar between the two groups4.
There is one important condition attached to that. It holds as long as you are not experiencing repeated episodes of your knee giving way. Repeated instability is the thing that does damage — not the absence of a graft. Which is exactly why ongoing giving-way is the signal to go back to the surgeon rather than to push on.
What happens if you try rehabilitation first?
High-quality trials comparing surgery with no surgery are hard to run and rare. Two of them matter here: the KANON trial1 and the COMPARE trial2. Both randomly assigned people with an ACL rupture to either early surgery, or rehabilitation with the option of delayed surgery if they needed it.
The results were consistent across both:
Roughly half of people managed without an ACL reconstruction.
Roughly half went on to have surgery, because of ongoing instability, pain, loss of function, or simply not trusting the knee.
A fifty-fifty split is not a small thing when the current default sends nine out of ten Australians to theatre.
There is a further detail worth knowing. Among the half who did not have surgery, around 30% showed evidence of ACL healing on their MRI — and a higher degree of healing was associated with better patient-reported outcomes3. Some ACLs heal on their own. We did not think that was true ten years ago.
Will I get back to my sport without surgery?
This is the question that stops most people from even considering it, and the evidence here has shifted.
It is growing increasingly clear that a person has a similar likelihood of returning to sport whether or not they have a reconstruction.
That runs so directly against the standard narrative that it is worth sitting with for a moment. The graft restores stability to the knee. It does not, by itself, restore the strength, the movement quality and the confidence that getting back to sport actually requires. Those come from the rehabilitation — which is the same work either way.
Reflecting on my own practice over the last seven or eight years, I have helped more people return after an ACL injury without surgery in the last twelve to twenty-four months than I did in the preceding five years combined. As a team we have returned athletes to high-level sport including touch football, surfing, skiing, skateboarding, AFL and soccer. The sentiment about whether reconstruction is compulsory is clearly changing, in Australia as well as overseas.
What if I try rehab and it does not work?
Then you have surgery, and you are not worse off for having waited.
Delayed reconstruction does not produce worse outcomes than operating straight after the injury. In fact, research suggests that one to six months of rehabilitation before surgery improves knee strength and function afterwards.
This is the part people find most reassuring once they understand it. Over a twelve-week trial of rehabilitation you have very little to lose except time — and the work you do in those twelve weeks is not wasted even if you end up in theatre. It becomes your prehabilitation.
The one thing that should not be tolerated during that period is repeated instability. If your knee is giving way, there should be a low threshold for going back to the surgeon.
Who is a good candidate for rehabilitation alone?
Working out whether this suits you takes a thorough examination, not a checklist off the internet. But these are the things that get weighed up, so you know what the conversation should cover:
Are there other injuries that need repairing? A large meniscus tear alongside the ACL changes the picture.
Are the other ligaments intact? An MCL injury on top of the ACL affects how stable the knee is likely to be.
Your age. Younger people are less likely to manage without a reconstruction.
Your activity level. The higher the demands you place on the knee, the lower the likelihood that rehabilitation alone will be enough.
Family history. A family history of ACL injuries suggests genetic factors are contributing, which tends to favour reconstruction.
The shape of your knee. Certain anatomical features, such as a steeper backward slope on the top of the shin bone, reduce the likelihood of managing without surgery.
How the knee behaves once you have done the work. Ongoing instability and poor function despite proper rehabilitation is the clearest signal of all.
Notice that most of these are not things you can assess yourself, and the last one cannot be known in advance. That is the honest answer to “am I a candidate” — some of it is knowable from your scan and your history, and some of it only becomes clear once you have given the knee a proper go.
It is also why a conversation with a doctor or physiotherapist who does a lot of this is worth having. This decision benefits enormously from someone who has watched it play out hundreds of times.
What trying rehabilitation alone actually involves
In most cases it is appropriate to trial at least twelve weeks of structured, progressive rehabilitation to find out whether you can regain enough stability and function to manage without surgery.
Three things are worth doing regardless of which way you are leaning:
Start rehabilitation. It is the common ingredient in all three pathways. Nothing about beginning good rehab closes a door.
Get an orthopaedic opinion anyway. I recommend this in every single case, even for people who are fairly sure they do not want surgery. You need the complete picture, including what else is going on in the knee.
Read up properly. The aclinjurytreatment.com decision aid was built by the team at the University of Melbourne specifically to help people make this choice, and it is not trying to sell you anything.
And then there are the upsides of not having an operation, which are easy to lose sight of when everyone around you assumes surgery is inevitable:
Avoiding surgical risks including infection, bleeding, blood clots, anaesthetic and scars.
No graft site problems, such as pain at the front of the knee or hamstring weakness.
Considerably less pain and discomfort, particularly through the first six to eight weeks.
Lower overall cost and less time off work.
The possibility that the ligament heals on its own.
The bottom line
Around half the people who try rehabilitation alone get through without an operation. Their arthritis risk is no different. Their risk of further damage is no different, provided the knee is not repeatedly giving way. Their likelihood of getting back to sport looks similar. And if it does not work, delaying surgery costs them nothing except time — and probably leaves them stronger going in.
That is a genuinely defensible option, and roughly nine out of ten Australians never get offered it.
None of that makes rehabilitation alone the right answer for you. It might not be. But it should be a decision you make with the numbers in front of you, rather than one that gets made by default in the first week while you are still in shock.
If I tore my ACL and was not eligible for cross bracing, I would try a period of rehabilitation to see whether I could manage without a reconstruction. That is a personal view about my own knee, not a recommendation for yours.
Not sure whether you need the operation?
That is exactly the conversation our Sports Knee Program is built around. We assess the knee properly, measure where it actually is, and give you a straight answer about what your options look like — including telling you when we think surgery is the better path. Return to sport testing is how we know whether the knee is genuinely ready, rather than guessing from a calendar.
We see patients across the Gold Coast at Robina, Currumbin and Benowa. You can get in touch with our team or phone 0408 051 943.
Frequently asked questions about ACL surgery and rehabilitation alone
Can you live a normal life without an ACL?
Many people do. In the two major randomised trials comparing the approaches, roughly half of the people assigned to rehabilitation first managed without ever having a reconstruction.
The deciding factor is usually whether the knee feels stable during the things you want to do. If it gives way repeatedly, that is the point at which surgery becomes the sensible option.
Will I get arthritis if I do not have ACL surgery?
Your arthritis risk appears to be about the same either way. A systematic review with at least ten years of follow-up found no difference in osteoarthritis risk between people who had surgery and people who did not.
This surprises most people, because avoiding arthritis is one of the most commonly cited reasons for having the operation. The evidence does not support it as a reason.
Can I play sport again without an ACL reconstruction?
The evidence increasingly suggests the likelihood of returning to sport is similar whether or not you have surgery.
What matters far more is the quality and completeness of the rehabilitation, and whether your knee stays stable while you build back up. Both pathways require the same hard work at the same intensity.
How long should I try rehabilitation before deciding?
In most cases at least twelve weeks of structured, progressive rehabilitation is appropriate before making a call. That is enough time to see whether the knee can regain the stability and function you need.
The exception is repeated instability. If the knee is giving way, that conversation should happen sooner rather than waiting out the twelve weeks.
Does waiting make ACL surgery less successful?
No. Delayed reconstruction does not lead to worse outcomes than operating immediately after the injury.
Research suggests the opposite is closer to the truth — one to six months of rehabilitation beforehand improves knee strength and function after surgery. If you do end up having the operation, the work you did in the meantime counts.
Will my ACL heal on its own?
It might. Among people in these trials who did not have surgery, around 30% showed evidence of ACL healing on MRI, and those with a greater degree of healing tended to report better outcomes.
If healing is something you specifically want to pursue, the timing is critical, and it is worth reading about the Cross Bracing Protocol quickly — that window closes within a few weeks of the injury.
Do I still need to see a surgeon if I want to avoid surgery?
Yes. I recommend an orthopaedic opinion in every case, without exception.
You need to know the full picture, including whether there are meniscus tears or other ligament injuries that change the recommendation. Getting that assessment does not commit you to anything.
Why does Australia do so many ACL reconstructions?
It is a mix of long-standing clinical culture, patient expectation and the sports we play. Around 90% of Australians who tear an ACL go on to reconstruction, which is among the highest rates in the world.
Elsewhere the default is different. In several Scandinavian countries — which keep excellent registries and can track outcomes properly — it is standard to wait three months before reconstructing.
What are the downsides of avoiding surgery?
The main one is that around half of people find rehabilitation alone is not enough, and end up having the reconstruction anyway a few months later than they otherwise would have.
For most people the cost of that is time rather than a worse result. The situation to avoid is pushing on through repeated episodes of the knee giving way, which is when the risk of further damage does rise.
Is rehabilitation alone cheaper than ACL surgery?
Generally yes — both in direct cost and in time away from work. That is one of several practical advantages, alongside avoiding surgical risks such as infection, bleeding and blood clots, and avoiding graft site problems like front-of-knee pain or hamstring weakness.
Cost should not be the deciding factor, but it is a real consideration and it is reasonable to weigh it.
References
1 Frobell RB, Roos EM, Roos HP, et al. A randomised trial of treatment for acute anterior cruciate ligament tears. New England Journal of Medicine 2010;363(4):331-42.
2 Reijman M, Eggerding V, van Es E, 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.
3 Filbay SR, Roemer FW, Lohmander LS, 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(2):91-98.
4 Lien-Iversen T, Morgan DB, Jensen C, et al. Does surgery reduce knee osteoarthritis, meniscal injury and subsequent complications compared with non-surgery after ACL rupture with at least 10 years follow-up? A systematic review and meta-analysis. British Journal of Sports Medicine 2020;54(10):592-98.
