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ACL- Anterior Cruciate Ligament. All you wanted to know

Lets talk about the Anterior Cruciate Ligament.


What is the ACL?

The anterior cruciate ligament (ACL) is one of four ligaments within the knee. The ACL is responsible for providing structural integrity of the knee when the knee is straightened and is responsible for controlling movement of the knee.


How do ACL injuries occur?

The big question I always wondered was;  how do so many athletes suffer such devastating injuries?  Well, a majority of ACL related injuries are non-contact injuries. Meaning, the injuries were sustained from sudden change in direction, landing or pivoting. As opposed to a contact injury such as a tackle.  Non- contact incidents make up 85% of  Male football players with  ACL related injuries (3). Furthermore, women are at a much higher risk of an ACL injury than men. There is no clear justification why, but is likely due to biomechanics, muscular strength and maybe hormone related(4).

How do you know if you have suffered an ACL injury?

Usually people often experience a pop or cracking noise with sudden instability. ACL injuries often cause sudden onset of pain and inflammation. However, sometimes pain is absent.  To ensure a correct diagnosis, see a physiotherapist or specialist Sports Doctor, . They will complete specific assessments to determine if the ACL is affected or not. This can then be confirmed with an MRI. An MRI is also a great tool for identifying any other potential injuries within the knee- eg meniscus, other ligament damage or bone bruising. X-rays demonstrate little clinical evidence to diagnose ACL injuries.  From there, a treatment plan will  be implemented. Plans may include non-operative  or operative treament of the knee. It will depend on the severity and complexity of the injury.

There is ever-growing evidence that supports both non-operative and operative management for such injuries. Collectively, both strategies emphasize the importance of reaching performance related targets to progress through the rehab process. Unfortunately, there is risk of re-injury to the ACL. This is regardless of manangment strategy. What does make a difference is the ability to pass the exercise based criteria.  Those that passed had 10% risk, compared to those that didn’t at 33% risk of re-injury (2).



Anterior Drawer test for ACL




It is important to get the rehab right. An ACL injury can result in longterm complications, which  can be quite devastating for the individual. An  ACL injury can lead to instability of the knee joint, reduce a person’s functional capacity, and lead to degenerative changes like osteoarthritis (1).   Firstly it depends on whether you have had surgery or not. Regardless, it is a step by step process, starting with very basic exercises. Initial work is to increase range and reduce swelling. While starting with lower level strength work. Certainly, the work load increases as you improve. Eventually they return to high level loads like plyometrics. An actual return to your sport is based on the requirements of the individual sport and your rehab progress.

Quite often you will hear about elite athletes having  accelerated rehab programs. Returing to their sport in a 6-12 month timeframe.  However, to do this requires daily work. Stringent following of the rehab protocol and regular reviews with specialists. Rehab is a challenging time for any individual.   Physical and mental resiliance affect progress. These can either speed up or slow down one’s recovery. Above all the most significant challenge to accept is that we all progress at different rates. It is integral to listen to our bodies and our rehab team.


Exercise Physiologist helping patient while completing low grade stretch and strengthen exercise

Can I reduce the risk of ACL injury?

Yes!  It is reported that ACL prevention programs can reduces all types of ACL injuries by 50% and can decrease non-contact ACL injuries in females by 67% (4)! That’s huge! Imagine playing a sport that had sudden changes in direction, jumping and landing, pivoting and not including any form of ACL injury prevention in your training program. But you ask, would what an ACL prevention program include? In a nutshell, I would include balance or proprioceptive work, lower limb strengthening, core strengthening and agility related drills that would include jumping, landing and changing direction.

My closing statement would be that I would strongly encourage any athlete who plays sport that requires jumping and landing, pivoting and changing of direction to include ACL prevention exercises and an appropriate warm up specific for ACL prevention. Moreover, if an injury is to be sustained affecting the ACL, I would strongly recommend commencing appropriate exercise management to reduce inflammation, regain functionality and range of motion and maintain or improve lower limb strength. Completing prehabilitation prior to surgical management would be most beneficial but determining whether surgery is necessary or not would be a discussion that should be had with your rehabilitation team.


  1. Chalmers, P., Mall, N., Moric, M., Sherman, S., Paletta, G., Cole, B., & Bach, B. (2014). Does ACL Reconstruction Alter Natural History?. The Journal Of Bone & Joint Surgery, 96(4), 292-300. doi: 10.2106/jbjs.l.01713
  2. Kyritsis, P., Bahr, R., Landreau, P., Miladi, R., & Witvrouw, E. (2016). Likelihood of ACL graft rupture: not meeting six clinical discharge criteria before return to sport is associated with a four times greater risk of rupture. British Journal Of Sports Medicine, 50(15), 946-951. doi: 10.1136/bjsports-2015-095908
  3. Waldén, M., Krosshaug, T., Bjørneboe, J., Andersen, T., Faul, O., & Hägglund, M. (2015). Three distinct mechanisms predominate in non-contact anterior cruciate ligament injuries in male professional football players: a systematic video analysis of 39 cases. British Journal Of Sports Medicine, 49(22), 1452-1460. doi: 10.1136/bjsports-2014-094573
  4. Webster, K., & Hewett, T. (2018). Meta-analysis of meta-analyses of anterior cruciate ligament injury reduction training programs. Journal Of  Orthopaedic Research®, 36(10), 2696-2708. doi: 10.1002/jor.24043

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