Discomfort at the front or inner knee area, which is aggravated by activity or by extended time sitting (such as at a desk chair or theater seat) with knees bent.

May be caused by overuse, injury, excess weight, a kneecap that is not properly aligned or changes under the kneecap.

The patella should be pulled up smoothly over the end of the femur in a straight line by the quadriceps muscle. Abnormal tracking allows the patella to grate over the lower end of the femur.

Knock-kneed and flat-footed runners and persons with an unusually shaped patella are at higher risk for this syndrome.

The main symptoms of patellofemoral pain syndrome are knee pain and chronic inflammation, especially when sitting with bent knees, running, squatting, jumping or using the stairs. The knee may be mildly swollen.

Occasional knee buckling/giving way may occur suddenly and unexpectedly due to lost quadriceps strength. Catching, popping, or grinding when walking or with knee movement is common. Pain tends to come on gradually and symptoms may increase over time.

Treatment is aimed to improve the alignment of the patella during contraction of the thigh muscle:

• Strengthening the inner quadriceps muscle
• Stretching and strengthening the quadriceps and hamstring muscle groups
• Bracing with patellar centering devices may be needed
• Icing, use of anti-inflammatory drugs and activity modification can help reduce irritation and pain