What Is the Patellofemoral Joint?
Definition: The patellofemoral joint is where the kneecap (patella) and thigh bone (femur) meet.

The underside of the patella sits in a groove within the femur called the patellofemoral groove. Within this groove, the patella moves largely lengthwise, but it has some side-to-side movement and can tilt and rotate as well.

Misalignment or repetitive contact of the joint surfaces may lead to patellofemoral pain syndrome. The result is joint irritation, inflammation, knee pain and limited range of motion in the knee.

Irritation of this joint is generally caused by the following factors:

  • Acute injury to the patella
  • Misalignment of the joint
  • Overuse from excessive running, particularly if there is an associated weakness of knee muscles
  • Chronic wear and tear of the knee joint
  • Poor foot mechanics
Patellofemoral irritation may also lead to breakdown of cartilage on the underside of the patella (chondromalacia), which in its most chronic condition, could require surgical repair.

Patellofemoral Pain Syndrome
Patellofemoral pain syndrome is also known as runner's knee

By Elizabeth Quinn, About.com Guide  Updated March 12, 2010

What Is Patellofemoral Pain Syndrome ?

One of the most complex joints in the human body, the knee, is prone to a variety of sports related injuries. One of the more common is Patellofemoral Pain Syndrome. This term usually refers to pain under and around the knee cap. The pain tends to worsen with activity, while descending stairs and after long periods of inactivity. Pain may occur in one or both knees. Patellofemoral pain syndrome is often mistaken for chondromalacia, a condition which describes damage (typically softening) of the articular cartilage on the underside of the kneecap.

While the exact cause of patellofemoral pain isn't known, it likely has something to do with the way the patella tracks along the groove of the femur. The patella can move up and down, side to side in the groove, as well as tilt and rotate. All this movement means that the patella can have contact with many of the articular surfaces of the knee depending upon a variety of factors such as muscle strength and balance, overuse, and incorrect tracking. It also means that the cause of the pain may be from a variety of different factors.

Despite all the things that may cause the pain, there are specific things you can do to combat patellofemoral pain. Rest is one of the first lines of defense. Turn to non-impact exercise, such as swimming, to keep your fitness level while allowing your knees to heal. While dedicated individuals can manage their own rehab program, ideally you would want a physician or physical therapist to coordinate your specific treatment plan. Depending upon the results of your diagnosis, there may be additional strengthening and stretching exercises you will need to add to your routine.

One reader wrote in regarding his own PPS, saying:
"In my own case, tight ITBs and muscular tightness contributed, but the most significant factor was the imbalance between my vastus lateralus (strong) and my vastus medialus (weak, along with the adductors). Various exercises and weight training options can help (and have in my case) to ameliorate this imbalance -- and fairly quickly!" Such imbalance can best be determined by a specialist. They will do muscle balance testing and determine what, if any, imbalance you may have. One of the strengthening exercises you would likely begin is for the quadriceps group to build the muscles that are responsible for the way the kneecap tracks.

The footwear your choose, can also be an important factor in recovering from PPS. High quality shoes should be replaced every 300 to 500 miles for a runner. Shoe breakdown can result in more knee pain. Orthotics and arch supports may also be advised. Icing the knees after use, has also been shown to decrease the inflammation, and pain in the joints.

Also see: chondromalacia.

Patellofemoral pain can be hard to treat, and may take considerable time (up to six weeks) to fully recover. So ease back into an exercise routine and maintain quadriceps strength, wear appropriate footwear, and rest at any signs of overuse, and PPS is far less likely to sideline you in the future.


The American Academy of Family Physicians Web Site, Patellofemoral Pain Syndrome Patient Handout, November, 1999. Last accessed March 2010

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