A knee dislocation is a severe injury where the bones of the knee joint are completely displaced from their normal alignment. This condition is distinct from a dislocated kneecap (patellar dislocation), which involves only the kneecap moving out of its groove. A knee dislocation is considered an orthopedic emergency due to its potential for serious complications that can significantly impact long-term function and even threaten the limb. The injury often involves extensive damage to ligaments and other soft tissues, leading to instability and considerable pain.
What a Knee Dislocation Is
A true knee dislocation occurs when the tibia (shin bone) completely separates from the femur (thigh bone) at the knee joint. High-energy trauma typically causes a knee dislocation, often rupturing at least three major ligaments that stabilize the joint. Common causes include motor vehicle collisions, falls from significant heights, and high-impact sports injuries. Even lower-energy incidents can cause dislocations in individuals with certain predispositions, such as morbid obesity or pre-existing knee weakness.
Upon dislocation, immediate and noticeable symptoms include severe pain, a visibly deformed or misshapen knee, and an inability to move the leg or bear weight on it. The joint may appear bent and unable to straighten, or it might present with significant swelling and bruising. Some individuals might also report hearing a distinct “pop” or “snap” at the moment of injury. About half of knee dislocations spontaneously reduce before a person reaches the hospital, which can sometimes mask the initial severity.
Immediate Response and Emergency Care
The severity stems from the high risk of damage to critical structures surrounding the knee, including blood vessels and nerves. The popliteal artery, located behind the knee, is particularly vulnerable, with injury occurring in about 20% of cases. Undetected vascular injury can lead to irreversible damage and may necessitate amputation if not treated within six to eight hours.
When a knee dislocation is suspected, it is important not to attempt to move the injured leg or force the joint back into place. Such actions can worsen existing damage to nerves, blood vessels, and surrounding tissues. Instead, the leg should be kept still and supported, preferably with padding, while emergency services are contacted immediately. Rapid transport to a hospital is paramount for a thorough evaluation and prompt intervention to mitigate potential limb-threatening complications.
Treatment and Recovery Process
Upon arrival at the hospital, medical professionals prioritize realigning the dislocated bones, a procedure known as reduction. This can often be performed manually (closed reduction) after administering pain relief and sedatives. In some complex cases, surgical intervention may be needed for realignment. Following reduction, immediate assessment for vascular and nerve damage is performed, often including imaging tests like X-rays, MRI, and angiography to evaluate blood supply.
After the knee is reduced and any urgent vascular or nerve issues are addressed, the recovery process typically begins with a period of immobilization using a brace or splint to stabilize the joint. This initial phase allows injured ligaments and soft tissues to begin healing. Physical therapy is then introduced, focusing on restoring strength, flexibility, and range of motion. Rehabilitation exercises often include strengthening the quadriceps, hamstrings, and hip muscles to improve knee stability.
Many knee dislocations involve significant ligament tears, often requiring reconstructive surgery to repair the damaged structures. The recovery timeline varies depending on the injury’s severity and whether surgery was performed, but it is generally a lengthy process. While some individuals may regain basic function within 6-8 weeks, full recovery, especially for athletes, can take 9 to 12 months or even longer if surgery was required. Consistent adherence to physical therapy protocols is important for optimal outcomes and preventing re-dislocation.
Long-Term Outlook and Potential Issues
Despite comprehensive treatment, a knee dislocation can have significant long-term implications, directly impacting a person’s quality of life. Many individuals may experience persistent knee instability, even after surgical repair and extensive rehabilitation. This can manifest as a feeling of the knee “giving way” or a general lack of confidence in the joint’s stability during activity. The extensive trauma to the joint surfaces and supporting structures also increases the risk of developing post-traumatic arthritis later in life.
Chronic pain and stiffness are common complaints following a knee dislocation, with some degree of dysfunction often remaining even after treatment. The risk of re-dislocation is also a concern, particularly if the initial injury caused significant damage or if rehabilitation is not fully completed. Nerve damage, especially to the common peroneal nerve, can result in persistent issues like foot drop, which can significantly impair mobility. While many patients achieve a reasonable level of function, returning to pre-injury levels of athletic performance can be challenging, with successful returns to high-level sports reported in a minority of cases.