Arthritis of the knee cap, also called patellofemoral arthritis, is a common cause of pain at the front of the knee. The cartilage behind the knee cap (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. Therefore, when the knee bends, the knee cap glides on the femur allowing smooth movement.

How do we diagnose arthritis in knee cap? 

Generally, arthritis in knee cap causes the following symptoms:

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

Importantly, your doctor must exclude other causes of pain in the front of the knee. Examples include patellar tendonitis, fat pad impingement, pes anserine bursitis, and meniscal tears. 

Often, imaging is helpful to confirm the diagnosis. For example, an X-ray, ultrasound, or MRI can look at the patellofemoral joint’s health and diagnose patellofemoral arthritis.

What are the treatment options for patellofemoral arthritis? 

brace for knee arthritis

Generally, we manage most knee cap arthritis pain with simple conservative measures. Firstly, 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

Sometimes, we use injections to help with knee cap arthritis pain in complex cases. Generally, options for injections include cortisone, hyaluronic acid,  platelet-rich plasma and Arthrosamid.

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 it does not work.

More on injections for patellofemoral arthritis

Platelet-rich plasma injections - alternative to cortisone injection in shoulder

Injections for knee cap arthritis can help in complex cases.

Cortisone injection for patellofemoral arthritis 

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 six 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. Cortisone injections for patellofemoral arthritis should be reserved for an acute flare of knee pain and swelling.

Hyaluronic acid injection for patellofemoral arthritis 

Next, we may 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 patellofemoral arthritis. In addition, unlike cortisone, the effect can last 6-12 months. Also, hyaluronic acid does not have the adverse effects on cartilage that cortisone has.

Generally, we suggest using a high molecular weight hyaluronic acid due to increased potency and a more significant duration of effect. An example of a high molecular weight hyaluronic acid is Durolane.

PRP injection for patellofemoral arthritis

Some doctors use platelet-rich plasma or PRP injections.

We get PRP from whole blood. We spin the blood in a centrifuge and separate the red and white cells. Then, the plasma is injected into the knee joint. We think PRP reduces inflammatory cells, improving pain and function. Overall, recent evidence suggests that PRP may be a bit better than hyaluronic acid. However, you often need more than one injection. Studies suggest two injections separated by 1-2 weeks are best for knee arthritis.

Arthrosamid for patellofemoral arthritis 

Arthrosamid is a non-degradable implant we inject into the knee joint to reduce pain and swelling from arthritis. The knee joint lining takes up the implant and reduces the inflammatory fluid the joint produces. It is a more expensive but potentially longer-lasting injection. However, we are still awaiting longer-term data showing Arthrosamid works better and longer than hyaluronic acid or PRP>

Final word from Sportdoctorlondon about arthritis in the knee cap

Knee cap arthritis is a common cause of pain in the front of the knee. Overall, most people improve with physiotherapy. Sometimes, we use injections to help. Generally, we recommend you start with a hyaluronic acid injection. 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.