A dislocation occurs when a bone is pulled or pushed out of its normal relationship to the other bones that make up a joint. It takes great force to dislocate a knee joint, and complete dislocation is uncommon. A dislocated knee joint requires emergency treatment.

Symptoms of a dislocated knee include:

• Severe pain.
• An odd, misshapen appearance or a bone that looks out of its normal position. The dislocated knee may look very different from the opposite knee.
• A feeling like something popped or feels out of place.
• Inability to bend or straighten the knee.
• Cool, pale skin or numbness and tingling in or below the affected knee.
• A feeling of severe instability.

Dislocation of the knee is a serious problem even if the bone pops back into place.

• Soft tissues in or around a joint, such as ligaments, tendons, muscles, and cartilage, may stretch and tear.
• Nerves and blood vessels can be damaged.
• A piece of bone at the base of the joint may break off and lodge inside the joint or cause a fracture that extends into the joint.

Immediate medical treatment may involve:

• Putting the bone back in place (reduction) if it hasn't already popped back in place.
• Splinting the joint.
• Immediate referral for further evaluation and testing to check blood vessels and nerves or for surgery to repair damage.