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Chondromalacia Patellae

Clinical Overview

Reviewed by Dr. Kevin Stone

Three bones meet in the knee: the thighbone (femur), the shinbone (tibia), and the kneecap (patella). When the leg moves, the kneecap slides along a shallow groove in the femur known as the trochlear groove. The joint is cushioned and made smooth by articular cartilage, which wraps around the ends of all the bones in the joint. Repeated abnormal stress of the joint, whether due to age, injury,abnormal alignment or muscle weakness, can weaken and soften the articular cartilage. Doctors estimate that about one-half of all non-injury knee pain complaints are due to this disorder.

When afflicted with the condition, the patient's knee rubs against the trochlear groove, instead of gliding smoothly across it. The damage may range from a slight abnormality of the surface of the cartilage to a surface that has been worn away completely to the bone. Anterior knee pain can present a diagnostic challenge because of the complex anatomy of the knee.

Note: There are other causes of anterior knee pain not considered here, which include scar tissue (plicae), patellar tendonitis and other soft tissue abnormalities.


  • Overuse when an abnormality exists
  • Chronic Injury
  • Muscle weakness (of the vastus medialis)

Risk Factors
Risk factors include participation in high-impact sports like running, skiing, soccer and high-impact aerobics when a previous abnormality exists. These sports do not cause chondromalacia themselves. Trauma to the front of the knee can cause a cartilage injury.. The Q-Angle, the angle formed by the thighbone and the patellar tendon (the misnamed ligament that stretches from the kneecap to the shinbone) is also a major factor in the development of anterior knee pain syndrome. Quickly-growing teenage women most often have a more acute Q-angle than others, and are thus at the highest risk group for developing the condition. Old age and a knock-kneed or bow-legged stance also increase the risk for developing anterior knee pain syndrome.

Last updated: Jan-01-09


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