The kneecap or patella is a small, triangular bone in the front of your knee that moves with the knee as it flexes. It glides up and down along a track at the end of the thighbone (femur) and gives the front thigh muscles (quadriceps) extra leverage for straightening the leg. The patella also protects the other bones in the knee against collisions and falls.
Patellofemoral pain syndrome occurs when the patella cartilage becomes overloaded due to overuse (often caused by high-impact activities) or as a result of poor alignment. High-impact sports — such as football, basketball, soccer, tennis and running — can aggravate existing abnormal kneecap alignment. In addition, running on uneven surfaces, like hills or trails, or playing on multiple surfaces (such as going from a grass to a hard court in tennis) also may increase the likelihood of patellofemoral pain.
The most common symptom of patellofemoral pain syndrome is a dull ache underneath the kneecap while walking down stairs, squatting or getting up after sitting for long periods of time. In addition, your knee may catch when bending, and you may experience a painful grating or creaking sensation.
Although many active people notice symptoms when starting new activities or increasing their level of intensity, especially with respect to high-impact sports, non-active people can suffer patellofemoral pain during routine daily activities as well.
Your doctor will likely ask when you noticed your knee pain, how it has been feeling since the pain began and if you've injured your knee before. He or she also may ask about any other conditions you have, such as diabetes and allergies, and if you are currently taking any medications.
Your doctor will assess the injury by feeling the knee area. Because the kneecap is easily accessible, he or she can quickly test for pain and tenderness by moving your kneecap and check how well it tracks as you flex and extend your leg. After this brief exam, your doctor most likely will be able to tell whether your discomfort is due to patellofemoral pain syndrome or another knee problem.
Eighty to 90 percent of people suffering from patellofemoral pain recover fully and are able to resume their previous activities. Most active people respond to non-surgical treatments. Surgery is prescribed only in rare cases when patellofemoral pain cannot be eased with braces, rest or physical therapy.
Depending on the amount of malalignment, you typically will be asked to try a well-supervised rehabilitation program for six weeks to six months. In most cases, you will need to continue the exercises you learn in physical therapy for life, which include specific movements for strengthening the knee, hamstring and calf muscles. If your patellofemoral pain continues, surgery may be recommended, although this is relatively uncommon.
Reviewed by health care specialists at UCSF Medical Center.