Anterior Cruciate Ligament tears occurs when the anterior cruciate ligament (ACL) is either stretched, partially torn, or completely torn. The most common injury is a complete ACL tear. Symptoms include pain, a popping sound during injury, instability of the knee, and joint swelling. Swelling generally appears within a couple of hours. In approximately 50% of cases, other structures of the knee such as surrounding ligaments, cartilage, or meniscus are damaged.
The underlying mechanism often involves a rapid change in direction, sudden stop, landing after a jump, or direct contact to the knee. It is more common in athletes, particularly those who participate in rugby, football (soccer), squash or netball.
Diagnosis is typically made by physical examination and is sometimes supported by magnetic resonance imaging (MRI). Physical examination will often show tenderness around the knee joint, reduced range of motion of the knee, and increased looseness of the joint.