Kneecap (patella) dislocation, or patellar subluxation, occurs when the triangle-shaped bone covering the knee (patella) moves out of place. This is a common occurrence in young athletes, especially females.

What causes kneecap dislocation?

Most commonly, the kneecap (patella) dislocates due to a twisting stress to the knee. However, the injury can also occur because of direct contact.

If a foot is planted and then a sudden twisting movement or rapid change in direction occurs, the stress to the knee can cause the kneecap to shift out of place. For example, if a runner suddenly changes directions, the force can lead to patellar subluxation or dislocation.

What does a dislocated kneecap feel like?

Symptoms of a dislocated kneecap (patella) include:

• Severe pain and an inability to walk
• Tenderness and swelling around the knee
• Sense of instability of the knee
• Collapsing of the knee, perhaps causing falls
• The kneecap physically slips to the outside of the knee

How do I know if I have a dislocated kneecap?

A physical examination by your doctor or orthopaedic provider is necessary to determine proper diagnosis. X-ray imaging of the patella may be required to rule out underlying conditions, including fracture.

Your doctor may also need to determine if the injury has caused damage to ligaments or cartilage in your knee. This can be done with magnetic resonance imaging (MRI).

How is kneecap dislocation treated?

Once kneecap dislocation is confirmed, the kneecap will be physically relocated or reduced -- i.e. pushed back into place.

After the kneecap is reduced and it has been confirmed that there is no fracture or damage to the knee's cartilage, your knee may be placed in an immobilizer or brace for several weeks.

Following a period of immobilization, physical therapy will then be recommended to build muscle strength and improve range of motion in the knee.

If the patella remains unstable and recurrent dislocations occur, arthroscopic or other surgery may be recommended to stabilize the patella. This may involve repairing the soft tissue or realigning the patella. 

If dislocations continue to occur and are left untreated, this can be detrimental, as kneecap dislocation can cause damage to your knee joint.

Treatment Videos

At Duke Orthopaedics, our knee specialists sometimes treat unstable patella with lateral release and medial imbrications or tightening of the ligaments and connective tissue on the inside of the patella.

The following video demonstrates this procedure.