I twisted my knee and heard a pop! Have I torn my ACL?
By Ronan Stapleton
Chartered Physiotherapist at Rehab Rooms Physio Clinic
Introduction
The dreaded ACL tear (Anterior Cruciate Ligament)! From your weekend warriors to your top professional athletes across a wide range of sports, it’s hard to escape! Whether you play rugby, soccer, tennis, Gaelic games, it can be a scary injury and a long rehabilitation and return to play process. As physios we see cruciate injuries regularly in practice, sometimes we see them soon after injury and they require ongoing referral to an orthopaedic consultant, sometimes we see them post surgery, sometimes people partially tear the cruciate but don’t end up needing surgery.
So what is the ACL?
The ACL is a ligament responsible for stabilising the knee joint. There are 2 cruciate ligaments, posterior and anterior, but the anterior cruciate is more often injured. Inside the knee joint, the two cruciate ligaments run from the top portion of the shin bone (tibia) to the bottom portion of the thigh bone (femur).
What does the ACL do and how does it get injured?
The specialised role of the ACL is to prevent the forward movement of the shin bone in relation to the thigh bone. So think of when you’re playing sport and your foot is fully planted on the ground but your body and thigh are pushed forward. It also has an important role in stabilising the knee when the body and thigh rotates around the shin bone – again think of your foot and lower leg fully planted but your upper body is twisting. Sometimes the force is too much for the ACL to bear and the ligament, stretches, tears or ruptures.
There are other structures that also help to stabilise and protect the knee from injury such as the medial and lateral ligaments (located either side of the knee) and the cartilage (located inside the knee on the surfaces of the bones). Unfortunately, these structures can also get injured if the force of the injury is bad enough – when they are injured together they can be referred to as the “unhappy triad”.
Is ACL injury caused by contact or non contact?
About two thirds of most cruciate injuries are caused by non-contact mechanisms like a sudden fast change of direction, a sudden deceleration, landing from a jump, twisting on a fixed foot. About a third are caused by direct contact such as a blow to the knee.
What would I feel if I injured the ACL (signs and symptoms)
In a lot of cases people can feel a “pop” in their knee with sudden pain. Depending on how bad the injury is, the knee can then suddenly swell and feel warm or this can happen later. The knee usually feels unstable and feels like it will give way.
What should I do if I get injured?
If you have the above symptoms you should be checked medically and often Xray is required initially to rule out a fracture (sometimes the ACL can pull off a piece of bone with it). This is usually followed by MRI to confirm the extent of the damage and to see if any other ligaments or tissues are injured.
Do I need surgery?
It really depends on how bad the injury is, your age, what kind of sport you play and the level that you play at. In some cases surgery is not required and people can function quite well with what we call a deficient ACL, once they fully rehab their knee and work hard on strength and stability. However, if you play multidirectional field sports, then surgery is often recommended. In recent years, there has been research to show ACL healing when locked in a brace at a certain angle but this may not be a viable option for everyone.
What is the role of Physiotherapy in ACL injuries?
I have seen a variety of ACL injuries in practice and each case requires the following:
1. Individual Assessment
No two injuries are the same. Have you had surgery or is it a non surgical ACL? What do you want to return to? What’s important to you? What did we find in assessment that needs to be worked on? A thorough assessment matches your injury to your goals.
2. Tailored Rehabilitation
If you have had surgery there are fairly well documented protocols that outline how long you will be on crutches, when to start different stages of rehab, when you can progress to the next stage. This depends on the type of surgery you have had and how things are progressing. There is a lot of emphasis placed on strengthening the quad muscles after ACL injury, and rightly so, however it is important to remember that the rehab process includes strengthening the entire limb ie calves, hamstrings, hips, core etc. In addition you need to train for improved co-ordination, stability and functional control. Finally you need to complete sports specific training and this typically occurs towards the end of the rehab process. These drills commonly include
hopping and jumping
graded exposure to accelerations, decelerations, changes of direction
gradual return to running at both low and high intensities
movements and skills specific to your sport
Evidence Based Rehab Tips
Early Mobilisation
Starting gentle basic movements and walking correctly with crutches early is really important for restoring range of motion. Sometimes this early stage of rehab is under utilised as the exercises can appear basic and often monotonous, but the initial phases of rehab lay the groundwork for the more challenging and functional rehab that comes later on.
Criteria Based Progression
It is important that rehabilitation is determined by criteria and not strict timelines. For example, progression from your acute rehabilitation phase to your strength phase doesn’t occur magically once you hit a 6 week marker, it comes when you meet certain targets eg normal walking pattern, full range of motion etc. For some people this may occur at 4 weeks, for others it may be 8 weeks. It also depends on your surgeons guidelines.
Stick to the plan!!
In my experience cruciate ligament surgery and rehab is very successful. However, the one mistake I see is when people do not complete their full rehab. Sometimes people skip the end stage strengthening and sports specific drills as they feel ok day to day but the demands of sport are very different than day to day activities. You need to train the body to cope with those demands. Re-injuring your ACL can occur up to 25% of people that have had surgery. Sometimes this can be just bad luck with getting another injury but sometimes the rehab just hasn’t been completed to a high enough level.
Summary
ACL injury and recovery can be a long process, but with the correct guidance and a bit of determination, it can be very successful and also presents an opportunity for you to return back to your sport even stronger than you were prior to injury.
What to Do Next...
At Rehab Rooms we believe that successful treatment is down to accurate diagnosis and assessment, which leads to successful treatment outcomes. With this in mind if you have had an ACL injury or surgery or any knee pain which is stopping you from doing your activities…why not book online by clicking here or call us at 01 430 5634 or simply send us an email at info@rehabrooms.ie to schedule a time that works for you!
About Ronan
Ronan is a chartered physiotherapist with a Masters in Sports and Exercise Medicine from Trinity College. Alongside his clinic work with us, he works with Leinster Rugby as a Regional Physiotherapist and was the Lead Physiotherapist for the Leinster U18 clubs in summer 2025. He also works with Clontarf U20s as their club physio. Ronan has previously worked in private practice and in the HSE so he brings with him a variety of clinical experience. Ronan is passionate about exercise medicine and believes in an active approach to rehabilitation alongside manual therapies to alleviate pain and discomfort. In his spare time, Ronan has a strong passion for Gaelic Football and captains his local club, Annanough GAA, in County Laois.
Note: the written content in this article is original. Some images are AI generated.