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Anterior cruciate ligament (ACL) injury – Should I have surgery or not?

Updated: Jun 8

If you’ve injured your anterior cruciate ligament (ACL), someone may have told you that you’ll likely need surgery to fix it. Or someone else may have told you that you don’t need surgery to fix it. Or you might not want surgery. In fact, being told different things by different people is one of the things that leads many to search for answers on Dr. Google.


How to decide if you should have ACL surgery or not.

Luckily for us mere mortals, a group of sixty-six ACL injury experts from eighteen countries have formed a working group named ‘Panther’ in order to provide a world-wide consensus on the current optimum management of ACL injuries, based on the most recent research evidence and their expert opinion.


The latest consensus from the ‘Panther’ group was published in July 2020 in the British Journal of Sports Medicine and provides some good advice on when surgery for an ACL injury is or isn’t a good idea. I have attempted to summarise some of this in normal language for normal people below.


My colleague Maryke Louw has also made a video about this:



Remember, if you need more help with an injury, you're welcome to consult one of our physios online via video call. 

Quick recap: What does the ACL do?

The ACL is one of the ligaments that attaches your femur (thigh bone) to your tibia (shin bone) at your knee.


The anatomy of the ACL and knee when looking from the front.

Its job is to keep the knee stable, limiting how much the tibia glides forward on the femur as you move your knee. It also helps to control rotation. Injuring it can sometimes cause the knee to give way, particularly when pivoting on it or turning quickly.

The ACL is usually injured by a non-contact twist of the knee. The most common description we physios hear is “my foot was stuck on the ground, I twisted, my knee went inwards and I felt (or heard) a sudden ‘pop’, I couldn’t continue. The knee swelled up massive within hours and now it doesn’t feel right.”

Only an MRI scan can definitively diagnose or disprove an ACL tear. I have seen many cases where patients have been told in A&E that they ‘definitely haven’t torn their ACL’, only to find out later on an MRI that they actually had torn it. Likewise, occasionally a knee injury can sometimes have all the hallmarks of an ACL tear, but then turns out to be something else, like a tibial plateau injury.


That said, if you fall into the category of somebody who would do well without surgery, then an MRI scan might not change how you manage the injury. In this case, it wouldn’t matter whether the ACL was officially torn or not, because your life would be fine anyway, just like all the people who injured their ACLs unwittingly in the past, were never diagnosed, and are now none-the-wiser.

Anyway, back to the topic. Should you have surgery or not? Here’s a summary.



Can an ACL injury heal on its own?


Yes, a recent study showed that ACL tears can heal without surgery.


The researchers also found that, two years after the injury, the patients whose ACL showed signs of natural healing on MRI reported less pain and better function than those who underwent surgery.


However, not everyone's ACL will heal on its own, and some people do require surgery. Researchers are not yet sure why some people's ACL injuries heal spontaneously and others don't.


When surgery is NOT required


Based on the current consensus, non-surgical management can be successful if:

  • The ACL is injured in the absence of any other concurrent injury (e.g. meniscus, cartilage, other ligaments);

  • There is no ongoing feeling of instability or giving way after completing a progressive, targeted and individualised rehabilitation programme* (more on this later);

  • The individual’s anatomical differences (e.g. the shape of an individual’s actual bones and joints, compared to someone else’s) are such that the knee is still quite stable despite the ACL injury;

  • The individual only wishes to return to ‘straight line’ activities, such as running, cycling, and swimming.


Benefits of not having ACL surgery


There are obvious risks associated with having surgery – e.g. risk of infection or graft failure, which are avoided if you can manage your ACL injury without surgery.


The rehabilitation period without surgery is quicker (usually about 3 months to return to sport) vs. after surgery (usually 6-12 months). This is because running is not recommended before 12 weeks post-op, as it often takes this long for the graft to be strong enough to tolerate running loads.


There is also the donor site to consider – if it is a hamstring graft, you will be sacrificing a hamstring tendon for it to be used for the ACL graft during surgery.



When surgery is recommended


An advantage of surgery is that there tends to be less ongoing laxity, so the knee is structurally more stable. However, this is obviously dependent on the skill of the surgeon.


The benefits of having surgery need to outweigh the risks for it to be an option.

Surgical management is recommended if:

  • You've also torn your meniscus, LCL or MCL;

  • The individual’s anatomical differences (e.g. the shape of an individual’s actual bones and joints, compared to someone else’s) are such that the knee is less stable with an ACL injury;

  • A targeted, progressive, individualised rehab programme* has been completed but the knee continues to give way;

  • The individual regularly plays sports involving jumping, cutting and pivoting e.g. football, rugby, basketball – as there is a higher risk of secondary injury on return to sports if managed without surgery;

  • There is ongoing instability / giving way on straight line activities despite rehab*.


ACL surgery might be the best treatment option in some cases.
ACL surgery might be the best treatment option in some cases.

*Targeted progressive rehabilitation


100% of the experts agreed that both post-operatively, if surgically managed, or post-injury, if non-surgically managed, people need a progressive, targeted, and individualised rehabilitation programme to return to pre-injury activities.


There is also evidence that performing rehab exercises while waiting for your ACL surgery can improve your outcomes.


All ACL injuries require rehab regardless of how they are managed.
All ACL injuries require rehab, regardless of how they are managed.

Rehab should be split into phases:

  1. Acute – Eliminating swelling, restoring range of movement, activating key muscle groups, addressing other contributing individual biomechanical issues.

  2. Mid – Neuromuscular control, proprioception/balance, and stabilisation exercises.

  3. Late – Restore full strength, function, sport/activity specific movement patterns.


This is where a specialist physio guiding you through the rehab, tailoring it to your individual needs, and adapting the programme where necessary, can make a big difference compared with looking up ‘knee exercises’ on YouTube.

Sometimes the best interests of a team differ from the best interests of the individual, e.g. if the player’s best outcome would be from surgery, but the team want the player to try non-surgical first as the rehab is quicker, to get them back on the pitch more quickly. So, watch out.

So, there we have it. Both surgical and non-surgical management have their merits, but it depends on the individual’s circumstances as to which is the best approach for them. It’s important that this decision is guided by both the individual and by a healthcare professional.

Whether managed surgically or non-surgically, the rehab is really important, and needs to be done well to have a good outcome.


Does it increase my risk of osteoarthritis if I don't have ACL surgery?


In the past, it was thought that ACL surgery reduced the risk of developing osteoarthritis in the knee, but they have since found that this is not necessarily the case. Development of osteorarthritis is multifactorial, and there are many contributing factors other than whether or not someone has had surgery for their ACL tear.


Does it increase my risk of injuring my meniscus if I don't have ACL surgery?


Sometimes. If you want to get back to a sport that involves a lot of pivoting and changing of direction, it might increase your risk of injuring your meniscus if you don't have ACL surgery.


However, if you're not interested in doing those sports and your knee feels stable after completing your rehab, the research shows that your risk of a meniscus tear is low.

How we can help


Need more help with your injury? You’re welcome to consult one of the team at SIP online via video call for an assessment of your injury and a tailored treatment plan.

The Sports Injury Physio team

We're all UK Chartered Physiotherapists with Master’s Degrees related to Sports & Exercise Medicine or at least 10 years' experience in the field. But at Sports Injury Physio we don't just value qualifications; all of us also have a wealth of experience working with athletes across a broad variety of sports, ranging from recreationally active people to professional athletes. You can meet the team here.

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Steph Davies

About the Author

Steph is a chartered physiotherapist with more than 15 years' experience and a Master’s Degree in Sports and Exercise Medicine. You can read more about her here, and she's also on LinkedIn.



References:

  1. Diermeier TA, Rothrauff BB, Engebretsen L et al (2020) Treatment after ACL injury: Panther Symposium ACL Treatment Consensus Group British Journal of Sports Medicine doi: 10.1136/bjsports-2020-102200

  2. Richard B Frobell (RB), Roos HP, Roos EM, Roemer FW, Ranstam J, Lohmander LS (2013) Treatment for acute anterior cruciate ligament tear: Five-year outcome of randomised trial BMJ 2013; 346 doi: https://doi.org/10.1136/bmj.f232

  3. Saueressig, T., Braun, T., Steglich, N., Diemer, F., Zebisch, J., Herbst, M., ... & Belavy, D. L. (2022). Primary surgery versus primary rehabilitation for treating anterior cruciate ligament injuries: a living systematic review and meta-analysis. British journal of sports medicine, 56(21), 1241-1251.

  4. Filbay, S. R., Roemer, F. W., Lohmander, L. S., Turkiewicz, A., Roos, E. M., Frobell, R., & Englund, M. (2023). 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, 57(2), 91-99.

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