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Anterior Cruciate Ligament (ACL) Tear Guide

An ACL tear is a common sports injury affecting the knee and is characterised by the tearing of the Anterior Cruciate Ligament, which is an important structural stabiliser for the knee. A ligament is a strong bond of connective tissue which attaches bone to bone, the ACL is situated within the knee joint and is responsible the back of the femur to the front of the tibia.

The Knee & ACL The ACL is one of the key ligaments of the knee, as it provides stability by preventing lateral movement, hyperextension and forward movement of the tibia on the femur. When these movements are excessive and become beyond of the ACL’s capability then a tear will occur. The severity of this tear can vary from a small tear which will cause a small amount of discomfort, to a complete rupture of the ACL which would cause a large amount of pain as well as needing a rehabilitation as well as potential surgery. 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 happen in activities which place an excessive amount of strain on the ACL, more commonly this occurs suddenly due to a specific incident, however, an ACL tear can be caused by repetitive strain occasionally. There are three main movements which place stress on the ACL:

  • Twisting of the knee
  • Hyperextension of the knee
  • Forward movement of the tibia on the femur

When any of these movements, or a combination of these movements occur to a level which the ACL cannot withstand, tearing of the ACL may occur. Twisting of the knee, is the most common cause of an ACL tear. ACL tears are seen frequently in contact sports, or sports which require a quick change in direction such as skiing. A twisting movement during a change of direction when weight-bearing or a collision forcing the knee to bend in the wrong direction are usual causes of an ACL tear. If you are looking to continue to exercise with a damaged ACL, we recommend using a Donjoy Armour Knee Brace, this brace will fulfil the function of your ACL meaning you can continue to do the sport you love. Signs & Symptoms of an ACL Tear Anyone who suffers an ACL tear may hear an audible snap or tearing sound at the time of the injury. In minor cases, some people will be able to continue activity only to experience an increase in pain, swelling and stiffness in the knee after the activity. If the ACL is completely ruptured there will be a moment of intense pain at the time of the incident, but the sufferer may find that is subsides quickly. Within a few hours the area will often swell and there may be unnatural movement of the knee joint due to its instability. The knee will likely collapse under any strain or movement and will become bruised and stiff within a few days of the incident.