Patellar Instability

What is patellar instability?

Patellar instability occurs when the kneecap (patella) moves out of its normal position in a groove (the trochlear groove) in the thighbone. As a result, the kneecap partially or completely dislocates.

The kneecap normally slides smoothly in the groove, which guides and stabilizes the kneecap's movement, keeping it centered in the joint and preventing dislocation.

Without treatment, knee instability doesn’t improve, making it easy for the kneecap to dislocate in the future. Dislocations happen more frequently the longer the condition remains untreated, causing chronic instability that affects knee function and stops you from enjoying your favorite activities.

What causes patellar instability?

Several conditions can lead to knee instability, including:

• Previous patellar dislocation
• Direct blow to the kneecap
• Ligament injuries (especially damage to the medial patellofemoral ligament (MPFL)
• Genetic conditions causing loose ligaments
• Groove that’s too flat to hold the kneecap
• High-riding kneecap that doesn’t fit in the groove properly
• Knock knees (knees bend inward)
• Abnormal rotation in the thigh and/or shinbone
• Patellar tendon attached to the shinbone in the wrong location

Knee dislocations and other injuries damage the ligaments. If the ligaments don’t fully heal and regain their pre-injury strength, they remain weak and can’t stabilize the joint. This creates ongoing patellar instability and frequent dislocations.

What are the symptoms of patellar instability?

Knee instability typically causes:

• Pain or swelling behind the kneecap
• Knee feels wobbly or like it could buckle or dislocate
• More frequent dislocations

When the kneecap dislocates, you may experience:

• Intense knee pain
• Knee buckling
• Audible pop
• Bruising
• Knee locking
• Inability to walk

You may be able to see that the kneecap is out of place.

How is patellar instability treated?

If your knee has dislocated, Dr. Ihn begins by returning it to its proper position. Then, treatment typically includes knee immobilization with a splint or brace and physical therapy.

Surgery is the next step if the instability doesn’t improve, you have more than one dislocation, or a piece of bone or cartilage is free-floating in the knee. During surgery, Dr. Ihn can reinforce the ligaments, correct poor bone alignment, and reshape the groove.

In addition to relieving your pain and restoring stability, surgery delivers other benefits, including:

• Lowering the risk of ongoing partial and complete dislocations
• Helping you return to athletics and daily activities
• Preventing arthritis by protecting the cartilage underneath the kneecap

If your knee has dislocated or feels unstable, don’t wait to seek help. Call Hansel E. Ihn, MD, or request an appointment online today.