Injuries to anterior cruciate ligament, or ACL, in the knee is a sports injury that requires specialised treatment. In this article, Dr Ralph Rogers of The London Sports Injury Clinic describes how the injury can occur, and the correct diagnosis, treatment and rehabilitation of the injury.
What is the anterior cruciate ligament or ACL?
The anterior cruciate ligament, commonly referred to as the ACL, is one of four ligaments that supports and stabilises the knee. The ACL works alongside the PCL (posterior cruciate ligament) joining the top end of the shin bone (tibia) to the bottom end of the thigh bone (femur). It help keeps the tibia from moving too far forward, dislocating the knee. It also keeps the tibia and knee from twisting around and rotating.
How ACL knee injuries occur
Ruptures or tears can occur to the ACL when it is forced beyond its normal working capacity. This often occurs during high impact sports and physical activity when a person stops suddenly, pivots, or lands flat on their feet. For example, if during sprinting someone comes to a quick stop, the force of their body (still moving forward) has to be absorbed to slow down the body. Under certain circumstances, the tibia can come forward too much which puts strain on the ACL, causing tears. ACL tears can also occur if sudden pressure is put on the lower leg from outside the body, causing the tibia to shift in an unnatural way. A common example of this in football is when another player slides in from the side and kicks the side or front of the leg.
An ACL injury can be anything from a sprain to a complete rupture. When a rupture occurs, a loud popping sound is sometimes heard, followed by immediate swelling and severe pain when bending the knee or trying to weight bear. The knee is usually very unstable afterwards and can suddenly “give way” during normal activity. It’s best to request an MRI to confirm the diagnosis and to determine if there are other injuries.
Immediately after the injury, as with many strains and ruptures, immediately apply the PRICE principle - Protection Rest, Ice, Compression, and Elevation - to reduce further immediate injury, pain and swelling. A knee brace may be used to support the joint while the ACL is resting and swelling reduces.
Anytime the ACL is torn, it affects the overall ability of the knee to stay stable and puts added stress on the remaining ligaments. Conservative (or non-surgical) management includes the use of braces and physiotherapy. A physiotherapist can help by providing exercises that will strengthen the surrounding muscles to provide additional support and prevent further injury.
The use of surgery as treatment
The decision to have surgery depends on many variables, including the person’s age, other health problems, the severity of the ACL injury, and the impact the instability has on the individual’s life. In saying that, most active people with ACL tears do not have surgery.
The surgery often uses part of a nearby tendon (patella tendon or hamstring tendon) to relocate it to the ACL site. This is usually done as an arthroscopic procedure and is less invasive than an open surgery and may require only one night hospital overstay, if any at all.
The rehabilitation programme is a crucial part of recovery and will have a huge impact on the effectiveness of the ACL reconstruction. Rehabilitation must be done by a trained physiotherapist, who will, over the months, decrease the swelling and increase the range of movement. They will also increase the strength of the quadriceps and hamstring muscle to avoid muscle imbalance that could be a risk for re-injury.