Understanding the Knee: ACL Sprain

What is it?  

A ligament is a strong but flexible band that joins two bones in a joint. The ligament plays a passive stability role by limiting excessive movements in unwanted directions.

However, the role of a ligament is not limited to passively ensuring the stability of a joint. Our ligaments have several nerve endings which are receptors informing us about the position of our joint in space; this is called proprioception. These receptors send signals that travel through our nervous system to our brain. Following the analysis of these signals, the brain sends instructions to the muscles around the joint in order to control the joint and avoid excessive movements which could lead to injury.

The anterior cruciate ligament (ACL) , for its part, connects the femur to the tibia at the knee. Its role is to limit and sense forward movement of the tibia in relation to the femur. This will help, along with the posterior cruciate ligament, limit excessive twisting of the knee.


Who could have it?  

Knee ligament injuries are common injuries found among athletes of all ages. The anterior cruciate ligament is the ligament most commonly affected, especially by a mechanism of injury that results in excessive twisting of the knee.

Alpine (downhill) skiing is a sport that requires good strength and control in the knees. Unfortunately, it is a common occurrence that a bad fall will lead to damage to the ACL. Often, injury can occur when the ski does not release from the boot as it should during a fall.


What does it look like?  

Injuries to the anterior cruciate ligament (ACL) therefore result in decreased passive knee stability and decreased proprioception.

There are different grades of ligament injury (or sprain) which vary according to the severity of the ligament damage.

  • A grade 1 sprain represents an elongation of the ligament fibers without a clear tear. It is then possible to have pain and a little swelling in and around the knee. The knee will not necessarily feel unstable, it may or may not feel like the knee is “giving way” .
  • A grade 2 tear corresponds to a partial tear of the ligament. It is possible to have small amounts of bleeding, which can lead to coloration in the leg. The knee will also have some tenderness and moderate swelling with loss of range of motion. The knee may appear unstable, loose or “give away” during activity.
  • A grade 3 tear is a complete rupture. There is more bleeding, tenderness, and swelling. The ligament cannot control the movements of the knee which seems unstable or loose. Often “giving away” with any rotational (pivot) movements.


How can physiotherapy help?

Grade 1 and 2 cases are almost always managed with physiotherapy treatments, surgery is rarely an option if the involvement is limited to the ACL. For grade 3 tears (complete rupture), physiotherapy treatment often allow of excellent recovery of function and the return to most sport. In these cases, physiotherapy treatments is the gold standard care in order to re-educate the strength and active control of the knee.

In some cases, despite optimal rehabilitation after a complete tear, significant functional instability persists with unpredictable “giving away” of the knee. In these cases, surgery becomes an option to consider. However, studies have shown that the better the knee has recovered before surgery, the easier it will be for rehabilitation after surgery. Today this rehabilitation before surgery is called “pre-habilitation” ! It is therefore essential after a grade 3 tear of the ACL to properly re-educate the mobility, strength and control of the knee, whether surgery is considered or not.

To conclude, current scientific evidence shows that physiotherapy treatments, before surgery, remain the treatments of choice for all grades of anterior cruciate ligament tears. Surgery is only considered after the initial physiotherapy has been done.

To prevent ACL injury: strengthening, balance and proprioception exercises are strongly encouraged during both the pre-season period and the sports season.


To learn more, do not hesitate to consult your physiotherapist!