What is patellofemoral syndrome?
Patellofemoral syndrome is one of the most common causes of chronic knee pain. It results from degeneration of cartilage due to poor alignment of the kneecap (patella) as it slides over the lower end of the thighbone (femur). This process is sometimes referred to as chondromalacia patella.
What causes patellofemoral syndrome?
The patella (kneecap) is normally pulled over the end of the femur in a straight line by the quadriceps (thigh) muscle. Patients with chondromalacia patella frequently have abnormal patellar "tracking" toward the lateral (outer) side of the femur. This slightly off-kilter pathway allows the undersurface of the patella to grate along the femur, causing chronic inflammation and pain.
Certain individuals are predisposed to develop patellofemoral syndrome:
- Knock-kneed or flat-footed runners
- Those with an unusually shaped patella undersurface
What are the symptoms of patellofemoral syndrome?
The symptoms of patellofemoral syndrome are generally a vague discomfort of the inner front of the knee, 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). Some patients may also have a vague sense of "tightness" or "fullness" in the knee area.
Occasionally, if chronic symptoms are ignored, the associated loss of quadriceps (thigh) muscle strength may cause the leg to "give out." Besides an obvious reduction in quadriceps muscle mass, mild swelling of the knee area may occur.
Diagnosis of patellofemoral syndrome
Patellofemoral syndrome is suspected in a person with anterior knee pain, especially in teenage females or young adults. With manual compression of the kneecap, while the quadriceps muscle is tightened, there can be a pain. This is referred to as the positive "shrug" sign. Generally, there is no associated swelling (knee joint effusion).
What is the treatment for patellofemoral syndrome?
The primary goal for the treatment and rehabilitation of patellofemoral syndrome is to create a straighter pathway for the patella to follow during quadriceps contraction. Initial pain management involves avoiding motions that irritate the kneecap. Icing and anti-inflammatory medications (for example, ibuprofen [Advil/Motrin] or naproxen [Aleve]) can be helpful.
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). Reviewing any changes in training before chondromalacia patella pain, as well as examining running shoes for proper biomechanical fit are critical to avoid repeating the painful cycle. Generally, full squat exercises with weights are avoided. Occasionally, bracing with patellar centering devices is required. Infrequently, surgical correction of knee alignment is considered.
Stretching and strengthening the quadriceps and hamstring muscle groups is critical for effective and lasting rehabilitation of the chondromalacia patella. "Quad sets" are the foundation of such a physical therapy program. Quad sets are done by contracting the thigh muscles while the legs are straight and holding the contraction for a count of 10. Sets of 10 contractions are done between 15-20 times per day.
What is the prognosis for patellofemoral syndrome?
Under optimal circumstances, the patient should have a rapid recovery and return to a fully functional level. Patellofemoral syndrome is not felt to be a precursor to degenerative arthritis (osteoarthritis).
Is it possible to prevent patellofemoral syndrome?
Patellofemoral syndrome can be prevented only in the sense that the symptoms can be prevented by avoiding any aggravating activities (running, jumping, etc.) or positions. Long-term prevention includes strengthening the inner portion of the quadriceps muscle to help normalize the tracking of the patella.
Koopman, William, et al., eds. Clinical Primer of Rheumatology. Philadelphia: Lippincott Williams & Wilkins, 2003.
Ruddy, Shaun, et al., eds. Kelley's Textbook of Rheumatology. Philadelphia: W.B. Saunders Co., 2000.
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