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Anterior Cruciate Ligament (ACL) injury to the knee – should I have surgery or not?

Updated: Jan 22, 2022

This article written by Steph Davies at Sports Physio Hwb Lampeter and aims to give you a guide to the pros and cons of surgery vs no surgery for anterior cruciate ligament injury of the knee, based on recent research evidence.


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 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.

Luckily for us mere mortals, a group of sixty-six world leading medical experts on ACL injuries, from eighteen different countries, have formed a working group named ‘Panther’ in order to provide a world-wide consensus on the current optimum management of ACL injury, 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 gives 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.

Quick recap: What does the ACL do?

The Anterior Cruciate Ligament is one of the ligaments that attaches your femur (thigh bone) to your tibia (shin bone) at your knee. 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 that they ‘definitely haven’t torn their ACL’ in A&E, only to find out later on an MRI that actually they had. Likewise, occasionally a knee injury can sometimes have all the hallmarks of an ACL tear, but it will turn 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.

When surgery is not required

There are obvious risks associated with having surgery – e.g. risk of infection or graft failure, that are avoided if non-surgically managed. The rehabilitation period without surgery is quicker – usually about 3 months to return to sport. The rehabilitation period after surgery is also longer, 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 – if it is a hamstring graft, you will be sacrificing a hamstring tendon for it to be used for the ACL graft.

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 ACL injury

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

When surgery is recommended

The advantages to having surgery is that (if done well) there tends to be less ongoing laxity, so the knee is structurally more stable. However, this is obviously dependent on the skill of the actual surgeon carrying out the procedure. The benefits of having surgery need to outweigh the risks, in order for it to be an option.

Surgical management is recommended if:

- The ACL and meniscus are both torn

- 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 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*

*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 follow in order to successfully get back to pre-injury activities.

Rehab should be split into phases:

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

Mid – Neuromuscular control, proprioception / balance, stabilisation

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.

Other considerations

- Sometimes the best interests of a team are different to 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, in order to get them back on the pitch quicker. So, watch out.

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


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 health care professional, such as a physio and specialist surgeon.

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

Let me know if you have any questions. You’re also welcome to consult me at our Sports Physio Hwb clinic in Lampeter for an individual assessment and rehabilitation plan.

Best wishes,



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

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:


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