Patellar Subluxation

What is a patellar subluxation?

A patellar subluxation (pronounced “suhb-luhck-SAY-shuhn”) occurs when your kneecap (patella) partially dislocates. It’s different from a patella (kneecap) dislocation, which means your kneecap has completely slid out of place.

Between your thighbone (femur) and shinbone (tibia), your patella slides up and down along a vertical groove called the trochlear groove. With a subluxated patella, it briefly pops outside of this groove. Most of the time, your kneecap will move toward the outside of your leg, but it can also slide toward the inside.

A subluxated patella can be very painful and make it uncomfortable to walk. Repeated patella subluxations increase your risk for arthritis, cartilage injury and overall instability of your knee, which can lead to other knee injuries. Even if your patella slides back into place, you should see your healthcare provider for treatment.

What are the symptoms of a patella subluxation?

Patellar subluxation symptoms may include:

• Visible deformity
• Severe knee pain
• Swelling
• Popping sound or sensation
• Buckling or catching of your knee
• Locking of your knee
• Instability of your knee
• Inability to squat or walk up and down stairs
• Feeling of your knee “giving away”

When you have a patella subluxation, your kneecap still tracks in the groove and you can still walk, but it may feel uncomfortable or unsteady, and you may hear a popping noise as it moves.

What are the complications or long-term effects of patella subluxations?

Patella subluxations often happen repeatedly. They also frequently lead to complete dislocations. In addition, the instability of your kneecap can cause damaged cartilage. Over time, this can contribute to knee osteoarthritis.

What causes patellar subluxations?

Injuries — like a direct blow to your kneecap — are the most common cause of patella subluxations. People who participate in contact sports like football are especially prone to the condition. It can also occur when you suddenly twist your knee while your lower leg is planted to the ground.

In addition, general looseness of the ligaments and tendons in your knee joint (patellar instability) can often lead to a subluxated patella.

What are the risk factors for patellar subluxation?

Patellar subluxations can affect anyone, but they’re especially common in people who have weak leg muscles and more tendon laxity. They’re also common in people who are:

• Between the ages of 10 to 20 years old
• Physically active
• Assigned female at birth
• Athletes or participate in sports
• Tall

If you’ve had a previous surgery for kneecap subluxation or dislocation, you have a higher chance of experiencing the condition again.

How is a patella subluxation diagnosed?

Your healthcare provider will perform a physical examination, bending and straightening your leg and palpating (feeling) around your kneecap. They’ll ask you about your symptoms, and they’ll also want to know what occurred that led to your kneecap sliding out of place.

Your provider may perform tests on your kneecap (subluxation tests), and they may request imaging tests, including:

• Knee X-ray
• MRI scan
• CT scan

How is a patellar subluxation treated?

Your healthcare provider may want to try conservative (nonsurgical) methods, especially if this is your first subluxation. Nonsurgical patellar subluxation treatment options include:

• RICE method. Rest, ice, compression and elevation.
• NSAIDs. Nonsteroidal anti-inflammatory drugs, like ibuprofen (Advil®).
• Immobilization. A knee brace or cast to keep your knee immobilized, depending on the severity of the injury.
• Walking/mobility aids. Crutches, a cane or a walker to keep weight off your knee, or the use of a functional knee brace, like a J-brace or patella-stabilizing sleeve.
• Orthotics. Special shoes to reduce pressure on your patella.
• Physical therapy. To help stretch and strengthen the muscles surrounding your knee and improve balance (proprioception).

If your symptoms continue for several months or you’ve had more than one patellar subluxation, your provider may recommend surgery. Surgical options include:

• Lateral release. A procedure that cuts the lateral retinaculum of your knee to improve patella positioning. It’s usually performed with other realignment procedures.
• Medial patellofemoral ligament (MPFL) repair. A procedure to repair and strengthen the ligaments that hold your patella in place.
• MPFL reconstruction. An arthroscopic surgery in which the medial patellofemoral ligament of your knee is reconstructed using your hamstring muscle.
• Osteotomy. A common procedure that involves cutting your tibia at certain angles for realignment of your tibia, patella, femur and connective tissues.

When should I see my healthcare provider?

You should see your provider if you have any symptoms that might indicate a patellar subluxation. Signs to look out for include:

• Pain and swelling
• An inability to put weight on your leg
• A popping or buckling sensation
• The kneecap appears to be popping out of its groove

What questions should I ask my healthcare provider?

Questions you may want to ask your provider include:

• What treatment options do you recommend?
• Will I need surgery?
• How likely am I to experience a recurrence?
• What can I do to prevent another subluxated patella?

How can I prevent patellar subluxation?

Injuries are the most common cause of patellar subluxation, and you can’t always prevent them. But there are ways you can keep the connective tissue that surrounds your kneecap strong. You can prevent a subluxated patella by:

• Getting physical activity that strengthens all your leg muscles
• Wearing knee pads when playing contact sports
• Wearing a knee brace to prevent injuring your kneecap again (if you’ve injured it before)
• Following your healthcare provider’s instructions if they’ve prescribed physical therapy

How long does it take to recover from a patella subluxation?

Recovery time for a subluxated patella depends on a few factors, including:

• If this is your first or a subsequent subluxation
• The severity of your condition
• What kind of treatment you received

If the subluxation was your first, it was minor and you didn’t need surgery, you may see a full recovery within four to six weeks. Your healthcare provider will likely recommend physical therapy, and your physical therapist can help you determine a timeline.

If you’ve had more than one subluxation, major damage or needed surgery, your recovery time will take longer. You may be able to resume light activities within six to eight weeks. But it could take a year or more before you’re able to play sports.