Patellofemoral syndrome (PFS): The commonest cause of chronic knee pain, PFS characteristically causes vague discomfort of the inner knee area, aggravated by activity (running, jumping, climbing or descending stairs) or by prolonged sitting with knees in a moderately bent position (the so-called "theater sign" of pain upon arising from a desk or theater seat). The knee may be mildly swollen. If chronic symptoms are ignored, the loss of quadriceps strength may cause the leg to "give out."
PFS is caused by an abnormality in how the kneecap (patella) slides over the lower end of the thigh bone (the femur). Normally, the patella (kneecap) is pulled up over the end of the femur in a straight line by the quadriceps (thigh) muscle. In PFS, there is patellar "tracking" toward the lateral (outer) side of the femur. This off-kilter path permits the underside of the patella to grate along the femur leading to chronic inflammation and pain. Females are at greater risk than males for PFS. Knock-kneed and flat-footed runners and persons with an unusually shaped patella are predisposed to PFS.
Initial pain management is icing, anti-inflammatory drugs (Advil/Motrin; Aleve) and avoiding motions which irritate the kneecap. Treatment and rehabilitation are designed to create a straighter pathway for the patella to follow during quadriceps contraction. Selective strengthening of the inner portion of the quadriceps muscle helps normalize the tracking of the patella. Cardiovascular conditioning can be maintained by stationary bicycling (low resistance but high rpms), pool running, or swimming (flutter kick). Changes in training that may have led to the PFS pain should be reviewed and running shoes examined for proper biomechanical fit to avoid repeating the painful PFS cycle. Occasionally bracing with patellar centering devices is required. Stretching and strengthening the quadriceps and hamstring muscle groups are essential to an effective and lasting rehabilitation of PFS. "Quad sets" are the foundation for such a program and are done by contracting the thigh muscles while the legs are straight and holding the contraction for a count of ten. Sets of 10 contractions are done between 15-20 times per day. Under optimal circumstances, there should be a rapid recovery and return at full functional level to sports.
PFS has also been called "housemaid's knee", "secretary's knee" and chondromalacia patella.