Patellofemoral arthritis happens when the joint behind your kneecap wears away. Treatment typically involves physical therapy and other conservative measures, but if you have more severe symptoms, you may need surgery.

Patellofemoral arthritis is a common cause of knee pain, especially in older adults. It develops where your patella (kneecap) makes contact with the end of your femur (upper leg bone) because the cartilage between your kneecap and femur wears away.

Most people can manage their symptoms conservatively with treatments like:

  • activity modification
  • physical therapy
  • steroid injections

If your patellofemoral arthritis does not respond to these treatments, you might need surgery. Surgery can range from minimally invasive procedures like chondroplasty to extensive procedures like a total knee replacement.

In this article, we examine the symptoms of patellofemoral arthritis and how doctors diagnose and treat it.

The primary symptom of patellofemoral arthritis is pain behind your kneecap. For most people, this pain develops when doing activities that put pressure on the kneecap, such as:

  • kneeling
  • squatting
  • going up and down stairs
  • getting up from low chairs
  • exercises like lunges or squats
  • bike riding

You might also:

  • have stiffness
  • have swelling
  • hear loud noises when you move your knee

If you have severe patellofemoral arthritis, your knee might get stuck when you try to straighten it.

Patellofemoral arthritis results from the loss of cartilage between your kneecap and a space at the end of your femur, called the trochlear groove.

Having a condition that changes the way your kneecap tracks may increase your odds of developing patellofemoral arthritis, such as:

  • Dysplasia: Dysplasia occurs when your kneecap doesn’t fit properly against the trochlear groove.
  • Kneecap fracture: Fracturing your kneecap can cause it to heal with a rough edge that rubs away cartilage.

Conditions associated with inflammation throughout your body can also lead to the breakdown of cartilage in your knee. Some of these conditions include:

People with patellofemoral arthritis frequently have a history of an unstable, loose, or misaligned kneecap.

Other risk factors include:

  • increasing age
  • obesity
  • history of patellar fracture
  • prior kneecap dislocation or subluxation (partial dislocation)
  • high intensity running or weightlifting
  • history of arthritis in other joints

People who experienced a dislocated kneecap during childhood may develop symptoms of patellofemoral arthritis as middle-aged adults. Without a previous injury, the condition tends to develop in older adults due to degeneration.

Doctors can diagnose patellofemoral arthritis with a combination of the following:

  • reviewing your medical history
  • asking you about your symptoms
  • performing a physical exam to:
    • inspect your knee for improper joint alignment
    • test your range of motion
    • assess the stability of your knee
  • requesting imaging tests such as X-rays or MRI scans

During your physical exam, your doctor may have you perform tests such as:

  • a step-down test, where you squat down on one leg on a short box
  • single-leg squats
  • flexibility tests
  • two-legged jump test
  • single-leg hop test

Stages of patellofemoral arthritis

Doctors often classify patellofemoral arthritis into four stages, based on how your joint looks with imaging:

  • Mild: You have more than 3 millimeters (mm) of joint space.
  • Moderate: You have less than 3 mm of joint space but no bony contact.
  • Severe: Your bony surfaces are in contact over less than a quarter of your joint.
  • Very severe: You have bony contact through your entire joint surface.
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Most cases of patellofemoral arthritis do not require surgery. Some of the most common nonsurgical treatments include:

  • Activity modification: Avoid activities that cause your symptoms to flare up, such as climbing stairs.
  • Weight loss: This may focus on losing weight if you have overweight or maintaining a moderate weight to reduce stress on your knees.
  • Physiotherapy: Physical therapy can help strengthen the muscles around your knee and take stress off your knee joint. There’s good quality evidence that physical therapy reduces short-term pain. Researchers are still studying long-term benefits.
  • Nonsteroidal anti-inflammatory drugs (NSAIDs): NSAIDs can potentially reduce swelling and inflammation.
  • Steroid injections: Steroid injections can help reduce swelling and inflammation.
  • Viscosupplementation: Viscosupplementation involves injecting a substance into your joint to improve your joint fluid. Researchers are still studying this treatment.

Several types of surgery are available to treat patellofemoral arthritis, including:

  • Chondroplasty: Chondroplasty involves trimming areas of cartilage to smooth your joint’s surfaces. It’s a minimally invasive procedure performed with a thin tube called an arthroscope.
  • Tibial tuberosity transfer: A surgeon slightly moves the bump in the front of your knee where your patellar tendon attaches to change the movement of your knee cap.
  • Patella realignment: A surgeon realigns or releases the tissue on either side of your kneecap to change its position.
  • Cartilage grafting: A surgeon takes cartilage from another part of your knee or from a donor to reduce friction between your kneecap and femur. Doctors usually reserve this procedure for younger people with small amounts of damage.
  • Patellofemoral replacement: A patellofemoral replacement is also called a partial knee replacement. A surgeon removes the damaged cartilage and a small amount of your femur. They attach a cover to the back of your patella and a piece of thin metal to your femur.
  • Total knee replacement: A total knee replacement is the most extensive surgical option. It involves replacing your entire knee joint with a prosthetic made of metal and other synthetic materials.

The outlook for people with patellofemoral arthritis varies significantly. It tends to have a relatively good outlook, and people can often manage it without surgery.

However, patellofemoral arthritis is progressive, meaning symptoms may worsen as degeneration continues over time. You may require more aggressive treatment as the condition progresses.

Factors that may cause you to require more aggressive treatment include:

  • advanced age
  • involvement of the joint between the femur and tibia (shin bone)
  • obesity
  • other chronic conditions

Here are some frequently asked questions that people have about patellofemoral arthritis.

Can patellofemoral arthritis be cured?

Patellofemoral arthritis and other types of osteoarthritis don’t have a cure. Some people can manage symptoms with conservative options or surgery.

Is patellofemoral arthritis serious?

Patellofemoral arthritis can cause symptoms that range from mild to severe and life altering. It tends to worsen over time, but some people can manage their symptoms with conservative treatment options alone.

Is patellofemoral arthritis painful?

Pain is the most common symptom of patellofemoral arthritis. Pain can range from mild to severe and is generally worse when you put pressure on your kneecap.

Patellofemoral arthritis is a common cause of knee pain. The most common symptom is pain behind your kneecap when you’re in positions that put stress on your knee.

Treatment typically involves physical therapy or other conservative options. A doctor may recommend surgery to treat more severe symptoms. Surgical options range from minimally invasive to total knee replacement.