Patellofemoral Pain Syndrome (Runner’s Knee)

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What is Patellofemoral Pain Syndrome?

Patellofemoral Pain Syndrome (PFPS) is a broad term used to describe pain in front of the knee and around the kneecap and in front of the knee that is typically an overuse pain with gradual onset and chronic duration.

What is the patella?

The knee joint is the largest hinged joint in the human body. It is made up of the lower end of the femur (thighbone), the patella (kneecap), and the upper end of the tibia (shinbone). The patella normally sits in a groove at the end of the femur called the trochlear groove. When you bend and straighten the knee, the kneecap moves up and down within the groove. As the knee bends and straightens, the quadriceps muscles and tendon help keep the kneecap sitting in the trochlear groove.

What causes patellofemoral pain?

PFPS is generally thought to be caused by increased pressure or joint overload on the patellofemoral joint due to a number of different mechanisms such as overuse and patellar malalignment.

Repeated stress on the knee, like from activities such as running, jumping, and squatting, can lead to patellofemoral pain. PFPS can also be caused be a sudden change in the frequency, intensity, or duration of physical activity, like running for longer distances.

PFPS can also be caused by abnormal tracking of the kneecap in the trochlear groove. If there is abnormal tracking, the patella gets pushed out to one side of the groove when the knee bends, causing increased pressure between the patella and the trochlea causing irritation leading to pain. There are a number of factors that contribute to poor tracking of the kneecap. If there is a problem with the alignment of your legs between the hips and the ankles, it may cause the kneecap to sit too high in the trochlear groove or to shift too far to the inside or outside of the groove. This causes the patella to rub on lower femur instead of gliding over it. Weakness or imbalance in the thigh or hip muscles,

Who does this affect?

Patellofemoral Pain Syndrome is the most common cause of chronic knee pain in young and middle age athletes and effects essentially everyone. It is more common in females than males, and is seen most frequently in adolescents and young adults.

What are the symptoms?

  • Knee pain behind, around, or under the kneecap, usually worse with activities that require bending the knee
  • Pain may be exacerbated by sitting with the knee bent for a prolonged amount of time. This is fairly characteristic of PFPS and even has it’s own name, the “theatre sign”.
  • Pain during activities that require repeatedly bending the knee, like jumping, squatting, or climbing stairs
  • You may notice a popping or crackling sound in the knee when bending then straightening it

How is patellofemoral pain syndrome diagnosed?

  • Your doctor can usually diagnose patellofemoral pain syndrome based simply on a history and physical exam.
  • To help determine the cause of the pain, your doctor will check a number of things such as the alignment of the lower leg and how the kneecap is positioned, knee stability, and the strength and flexibility of your hip and thigh muscles. Your doctor will also check your knee to see if there are any problems with patellar tracking and may want to examine your gait to see if this is contributing to the pain.
  • Your doctor may get an x-ray to rule out any damage to the structure of the knee itself or rule out other diagnoses such as boney cysts, masses, or joint abnormalities.

How is patellofemoral pain syndrome treated?

PFPS is usually best treated by a combination of rest, anti-inflammatories and ice, changing your activities, as well as a vigorous physical therapy or home exercise program.

Physical therapy or home exercise programs focusing on strengthening of the inner quadriceps, as well as the hip adductor, hip abductor and gluteal muscles can help correct problems with alignment and muscle balance. Flexibility and biomechanics are also critical factors to improve when doing rehabilitation for PFPS.

A patellar stabilizing brace can also be used to help the kneecap track correctly.

NSAIDS – non-steroidal anti-inflammatory drugs like ibuprofen or naproxen can help reduce pain and inflammation

When can I return to my sport?

Depending on the stage of overuse syndrome with PFPS one may be able to continue with modified activities or need to take 6-8 weeks off from running or their sport.  In general formal physical therapy is initiated if an athlete has more advanced stage and once the pain has resolved, you can gradually increase your activity level and transition back to your sport.


More about Common Running Injuries: Running and Jogging Injuries

By Elise Terry and Mo Mortazavi MD