Arthritis of the kneecap also called patellofemoral arthritis is a common cause of pain at the front of the knee. The cartilage behind the kneecap (patella) begins to wear out. When the cartilage is worn out, the bone rubs against the lower leg (femur) causing pain.

What is the patellofemoral joint?

patella arthritis

The patellofemoral joint makes up part of the knee joint. This part of the knee joint lies between the kneecap and the femur. When the knee bends, the knee cap glides on the femur allowing smooth movement.

How do we diagnose arthritis of the kneecap? 

Generally, arthritis behind the kneecap causes the following symptoms:

  • pain under kneecap, usually worse after sport or prolonged sitting
  • grinding or clicking with the movement of the knee
  • swelling of the knee joint

Importantly, your doctor needs to rule out other causes of pain at the front of the knee. Examples include patellar tendonitis, fat pad impingement, pes anserine bursitis, and meniscal tears. 

Often, imaging is useful to confirm the diagnosis. X-ray, ultrasound or MRI can be used to look at the health of the patellofemoral joint and to diagnose arthritis in kneecap.

What are the treatment options? 

brace for knee arthritis

Overall, we manage most people’s kneecap arthritis pain with simple conservative measures. Exercise therapy should be the basis of treatment. Examples of treatments that are effective include:

  • strengthening of the hip and knee
  • stretching of the muscles around the hip and leg
  • taping or bracing of the kneecap
  • using proper shoes and orthotics
  • medications such as ibuprofen

In difficult cases, we sometimes use injections to help with kneecap arthritis pain. Generally, options for injections include cortisone, hyaluronic acid, and platelet-rich plasma.

Finally, surgery should only be considered when all other treatments have failed. Moreover, joint replacement is the only effective treatment. You should avoid keyhole surgery for arthritis behind the kneecap as evidence suggests that it does not work.

More on injections and arthritis of the kneecap

Platelet-rich plasma injections

Injections can help in difficult cases. Traditionally, we have used cortisone injections for pain and swelling of arthritis. However, we know that cortisone injections are a short-term fix only. A recent study found that cortisone injections were similar to placebo injections for knee arthritis at 6 months. Also, there are a few concerning trends with repeat cortisone injections such as an acceleration of arthritis. Overall, we should avoid cortisone injections in most arthritis cases.

Next, we use hyaluronic acid injections. Hyaluronic acid is a natural substance found in bones, tendons, and joints. Injecting hyaluronic acid into joints reduces inflammation and pain associated with arthritis in kneecap. In addition, unlike cortisone, the effect can last for 6-12 months.

Finally, platelet-rich plasma or PRP injections have been used by some doctors. We get PRP from whole blood. We spin the blood in a centrifuge and separate the plasma from the red and white cells. Then, the plasma is injected into the knee joint. We think that PRP works by reducing inflammatory cells thereby improving pain and function. Recent evidence suggests that PRP may be better than cortisone or hyaluronic acid.

Most importantly, injections should be done with ultrasound to improve accuracy and effectiveness. We know that injections without ultrasound are less accurate and increase the risk of side effects.

Final word from Sportdoctorlondon about arthritis under kneecap

Kneecap arthritis is a common cause of pain at the front of the knee. Overall, most people improve with physiotherapy. Sometimes, we use injections to help. Finally, you should avoid surgery unless you are thinking about joint replacement. Keyhole (arthroscopy) surgery does not work.

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Dr. Masci is a specialist sport doctor in London. 

He specialises in muscle, tendon and joint injuries.

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