ACL is the abbreviation for the Anterior Cruciate Ligament. This is one of the major stabilising ligaments within the knee. It connects the femur (thigh bone) to the tibia (leg bone) and prevents abnormal movement (instability) occurring between the two. More specifically it provides rotatory stability to the knee to allow movements such as pivoting or sudden change in direction to occur without the knee giving way.
How does the ACL get injured?
The most common mechanism of injury is from a non-contact injury that typically occurs whilst attempting a pivoting or cutting (change of direction) manoeuvre during sport [Figure 1]. The injury can also occur from contact activity (e.g. being tackled from the side) when your knee buckles inwards whilst the leg is held in a fixed position. Not uncommonly, a “cracking or popping” sensation is felt at the time of the injury. The injury is associated with a lot of swelling within the knee that typically occurs at the time of, or soon after the injury. The leg is often painful to walk on for several days.
Figure 1. Picture of torn ACL
Other associated injuries
An ACL rupture may be associated with an injury to other stabilising ligaments within the knee. Rupture of your ACL is commonly associated with tears that involve the shock absorbing cartilages (menisci) of the knee. Depending on the location and size of these tears, they may be surgically repaired or trimmed at the time of your surgery. Bruising (oedema) of the bones also occurs at the time of injury because your femur and tibia are driven into each other by the violent forces that cause the ligament to rupture. No specific treatment is required for this “bone bruising”.
The first line of treatment following injury to the ACL should be those of the RICE principle (Rest, Ice, Compression, and Elevation). Early review by a physiotherapist is important to reduce swelling, improving movement and minimise wasting of muscles around the knee joint. Crutches are generally recommended to avoid excessive weight on the injured limb primarily during the early stages until you can walk without pain.
Goals Of Treatment
The treatment of ACL tears will vary across individuals based on their expectations, lifestyle, sporting aims etc. The major aim is to return the patient to their desired level of activity, both in regards to sport as well as other activities such as your occupation, whilst minimising the risk of injury to other structures within the knee.
Patients with an ACL tear who do not wish to return to pivoting sports can often be managed with this approach. Running in a straight line, swimming, bike riding and golf are activities that are suitable. Physiotherapy is critical in the recovery phase to restore movement and strength to the lower limb. The latter phase of your rehabilitation should focus on proprioceptive re-training. These are exercises that improve the protective reflexes around the joint to minimise further instability episodes and reduce the risk of further joint injury.
When is an ACL Reconstruction recommended?
Most patients who want to return to pivoting sports will require a reconstruction to prevent their knee buckling during these activities. Other indications for surgery include young patients with high activity levels and people who work in an environment where knee stability is critical for safety and function. If your knee is giving way regularly and this is interfering with your quality of life, you may want to consider an operation. This instability may occur during sport or during activities of daily living.
For information on ACL Reconstruction Surgery, click here.