An<unk>  occurs when the<unk><unk>  ligament (ACL) is either stretched, partially torn, or completely torn. The most common<unk>  is a complete tear. Symptoms include pain, an audible cracking sound during<unk> , 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 alpine skiing, football (soccer), American football, or basketball. 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. Prevention is by neuromuscular training and core strengthening. Treatment recommendations depend on desired level of activity. In those with low levels of future activity, nonsurgical management including bracing and physiotherapy may be sufficient. In those with high activity levels, surgical repair via arthroscopic<unk><unk>  ligament reconstruction is often recommended. This involves replacement with a tendon taken from another area of the body or from a cadaver. Following surgery rehabilitation involves slowly expanding the range of motion of the joint, and strengthening the muscles around the knee. Surgery, if recommended, is generally not performed until the initial inflammation from the<unk>  has resolved. About 200,000 people are affected per year in the United States. In some sports, females have a higher risk of ACL<unk> , while in others, both sexes are equally affected. While adults with a complete tear have a higher rate of knee osteoarthritis, treatment strategy does not appear to change this risk.
Anterior cruciate ligament injury
Tibial plateau fracture
Posterior cruciate ligament injury
Knee dislocation  Knee dislocation  1
Medial knee injuries
Pes anserine bursitis
Patellar dislocation
Patellar subluxation syndrome