Many people go to their doctor because they have knee pain. After a few inconclusive physical tests and a series of X-rays that did not turn up anything noteworthy, they are diagnosed with Patellofemoral Pain Syndrome (PFPS) — the most common diagnosis of exclusion made when dealing with knee pain of unknown origin.
PFPS affects several million Americans each year who are primarily between the ages of 15 and 55 years old with most of the cases occurring in a younger population. It is progressive in nature, beginning with slight discomfort and aching but can reach a point of intense pain and complete intolerance of exercise and activity — despite the lack of structural damage found on imaging studies and physical testing.
PFPS describes knee pain that does not have clear onset or consistent pattern of pain. It is characterized by pain that feels like it is directly behind the kneecap and the knee will ache or throb during periods of rest, usually improving with light exercises or movement. Patients with PFPS are typically unable to sit through an entire movie — called the "Moviegoer's Sign" — without getting up to move because of a pressurized feeling that builds up in the knee.
Because of these symptoms, Patellofemoral Pain Syndrome is often a deterrent to weight loss and a healthy lifestyle. The intensity of exercise needed to lose weight often exceeds the capabilities of someone with PFPS because of strength and pain reasons — thus perpetuating the cycle of pain.
Despite the inability of the battery of physical tests to point towards a diagnosis, PFPS does have some important clinical features that are easy to pick up with a routine physical therapy exam.
The first of these features is loss of hip strength. Loss of strength in a specific plane (lifting your leg out to the side) causes a significant inward rotation of your thigh bone during normal activities. If your hip strength is weak, activities that will produce the most pain are squatting, jumping, running and bending down to kneel.