What is an ACL tear?
An ACL tear is a common sports injury affecting the knee and is characterized by tearing of the Anterior Cruciate Ligament (ACL), which is an important structural stabiliser for the knee.
A ligament is a strong band of connective tissue which attaches bone to bone. The ACL is situated within the knee joint and is responsible for joining the back of the femur to the front of the tibia.
The Knee and ACL
The ACL is one of the most important ligaments of the knee. The ACL provides stability by preventing lateral movement, hyperextension and forward movement of the tibia on the femur. When these movements are excessive and beyond what the ACL can withstand, tearing to the ACL occurs. This condition is known as an ACL, however, the severity can range from a small tear that would cause discomfort, to a complete rupture of the ACL, causing a large amount of pain and requiring comprehensive rehabilitation and potentially surgery.
There are three grades of ACL tears:
Grade 1 tear: a small number of fibres are torn resulting in some pain, but allowing full function.
Grade 2 tear: a significant number of fibres are torn with moderate loss of function.
Grade 3 tear: all fibres are ruptured resulting in knee instability and major loss of function.
Causes of an ACL tear
ACL tears typically occur during activities placing excessive strain on the ACL. This generally occurs suddenly due to a specific incident, however, occasionally may occur due to repetitive strain. There are three main movements that place stress on the ACL, these include:
twisting of the knee
hyperextension of the knee
forward movement of the tibia on the femur
When any of these movements (or combinations of these movements) are excessive and beyond what the ACL can withstand, tearing of the ACL may occur. Of these movements, twisting is the most common cause of an ACL tear.
ACL tears are frequently seen in contact sports or sports requiring rapid changes in direction such as skiing. The usual mechanism of injury for an ACL tear is a twisting movement (change of direction) when weight-bearing (especially when landing from a jump) or due to a collision forcing the knee to bend in the wrong direction (such as another player falling across the outside of the knee).
When continuing to exercise with a damaged ACL we recommend the Donjoy Armor, as this brace essentially fulfils the function of your ACL, allowing even those with complete ruptures to their ACL to continue doing the sport that they enjoy.
Signs and Symptoms of an ACL tear
Patients with an ACL tear may hear an audible snap or tearing sound at the time of injury. In minor cases of an ACL tear, patients may be able to continue activity only to experience an increase in pain, swelling and stiffness in the knee after the activity.