Knee dislocation

A dislocated knee is often the result of a high impact injury such as a road traffic accident, a sporting injury or a serious fall. It can also be caused by a relatively minor injury, such as a missed step or unusual twist.

Among the symptoms of knee dislocation are:

• Extreme pain that is worsened by attempting to move the knee.
• Deformity of the knee joint.
• Shortening and misalignment of the lower leg.
• Obvious swelling.

A dislocated knee is a medical emergency and the joint will be repositioned as soon as you arrive in the emergency room. Once it is back in position, the surrounding tissues, nerves and blood vessels will need to be assessed for damage. It is highly likely that you will have tearing or rupturing of the anterior cruciate ligament and posterior cruciate ligament. You may also have damage to the cartilage, collateral ligaments and meniscus.

To diagnose the type and extent of these injuries you will be referred for an X-ray or CT scan which can show misaligned bones. An MRI scan may be used to assess the extent of damage to ligaments, tendons and cartilage. Your consultant may also order a CT angiogram, which is a special type of CT scan that uses an injection of dye into the vein to map blood flow. This can help to diagnose vascular obstruction. A Doppler ultrasound may also be used to assess arterial blood flow. Any nerve damage will be assessed using a physical examination to check for impaired foot movement or sensations of numbness or pain.

Initially, the priority is to minimise damage to blood vessels and nerves. Once these have been stabilised, damage to surrounding tissues can be addressed. A dislocated knee may require multiple surgical procedures to repair the extensive damage that can occur. These may be performed as arthroscopic (keyhole) surgery, using a tube-like instrument called an arthroscope, or open surgery which uses larger incisions.
You may require surgery to repair ligament and cartilage damage and meniscus tears . If you have arterial injuries you may be offered surgical repair using a synthetic patch, graft or transplanted vein. Alternatively you may need an arterial bypass or an embolectomy to remove a clot. If cartilage has been lost, you may need cartilage implantation or cartilage transfer.

After a knee dislocation you will require extensive physiotherapy and rehabilitation to restore knee function. Without proper rehabilitation, there is a risk of chronic knee stiffness, instability and post-operative nerve pain.