A hyperextended knee is an injury that occurs when the knee is bent backward, and extended past its normal range of motion. This is usually a result of a hard landing after a jump, or a trip and fall. Sharp pain is immediate when the knee is hyperextended. Ligaments, cartilage, and other stabilizing structures within the knee joint can be damaged. Hyperextension can range from mild to severe; in some cases, an ACL tear, knee dislocation, or other ligament or structural damage will result in a need for surgical repair.

Symptoms and Diagnosis

Immediate symptoms include: extreme pain, the sound of a pop, or a feeling that the knee has been thrown out of alignment. The majority of the pain will occur in the back of the knee, and swelling will follow within the first few hours after the injury. The knee may show signs of instability, and for athletes specifically, running or continuing to play sports will be almost impossible. For most patients, even walking may be difficult. Your physician will gather a detailed history and perform a careful physical examination. In addition, X-rays and an MRI will be required to confirm the exact nature of the injury.


Initial treatment for a hyperextended knee will include rest, crutches, and anti-inflammatory medication. Physical therapy may also be needed, prior to the surgery, in order to regain strength in the nearby muscles and to re-establish range of motion. If the anterior cruciate ligament or multiple knee ligaments are torn (knee dislocation), surgery will be required. Your physician will perform an arthroscopic knee surgery to repair or reconstruct the damaged cruciate ligaments (ACL and/or PCL), and because the collateral ligaments are on the outside of the knee, he may need to perform open surgery to reconstruct the collateral ligaments.


Following surgery, your physician will prescribe a thorough rehabilitation program. For athletes who wish to return to sports, it may take 6 to 9 months before full participation. Physical therapy will be a progressive process to help aide restoration of physical functions. The physical therapy will consist of exercises increasing range of motion, strength, and balance, so that overall stability can be restored to the knee.