What Is Patellofemoral Pain Syndrome?
Patellofemoral pain syndrome (PFPS) is a general term referring to pain in the knee. It is condition closely related to chondromalacia. The terms are often used interchangeably, and both are sometimes referred to as runner’s knee. However, chondromalacia is one of many possible causes of PFPS, not another name for the same condition.
Pain in the front of or around the knee is the main symptom of PFPS. The pain usually appears while:
- Kneeling or squatting
- Sitting for a long period
- Walking up or down stairs
Pain is also typically present after activity. Crepitus—a popping or cracking sound in a joint—is another possible symptom of PFPS.
Causes and Risk Factors
Overuse and misalignment of the kneecap are two common causes of PFPS. Overuse occurs when stress is placed on the knee over and over again. Athletes are prone to overuse, including those who participate in:
- Jogging or running
- Weightlifting, especially squatting
PFPS can frequently present when stepping up activity level, such as training more often or running/ biking longer distances. Office workers, drivers and others who sit for long periods are also at risk for PFPS, because of the strain placed on the knee due to the angle closing.
Patellar misalignment is another cause of PFPS (and chondromalacia). In a normal knee, the kneecap moves up and down in a depression on the end of the femur called the trochlear groove. Sometimes, the knee does not track in the groove correctly. Trauma to the kneecap can knock it askew from the trochlear groove, or muscle imbalances can pull it out of alignment. This can cause the cartilage on the underside of the kneecap to be scraped away over time.
Aside from sports and lifestyle, risk factors include age and gender. PFPS is more common in adolescents and young adults; knee pain in older people is more often caused by arthritis. Women are more likely than men to develop PFPS.
PFPS is what is known as a diagnosis of exclusion, meaning doctors rule out other conditions that could be causing the knee pain. If they’ve found no evidence of other conditions, they diagnose the problem as PFPS.
A physical exam is the cornerstone of a PFPS diagnosis. A doctor will gently manipulate the knee, asking the patient about where the pain is and how it feels (e.g., an aching pain versus a sharp pain). The physician will also try to determine if there was an acute injury or certain activity causing the pain, and when the patient feels pain most often.
An X-ray can be helpful in ruling out other conditions. X-rays do not display soft tissue such as cartilage, tendons or ligaments well, but can show damage to the patella or femur. A magnetic resonance imaging scan can detect any damage to the patella’s cartilage, indicating chondromalacia.
Most cases of PFPS can be successfully managed without surgery. Doctors will typically recommend starting with modifying or ceasing the activities causing pain. When a pain flare up happens, the RICE method is suggested first:
- Rest the knee
- Ice the knee
- Compression sleeve or bandage on the knee
- Elevate the knee above the heart to reduce swelling
Physical therapy and exercise can be helpful in correcting muscle imbalances that are pulling the knee off-track. Special shoe inserts called orthotics can cushion the impact of walking or running and help take pressure off the lower leg and knee.
Surgery is not typically necessary unless the PFPS causes severe pain and has not responded to more conservative treatments. Surgical options are usually arthroscopic—minimally invasive surgeries using small incisions, small tools and a flexible camera called an arthroscope.
Surgical procedures to correct PFPS can include:
- Debridement—clearing out damaged tissue
- Tendon release—loosening a tight tendon that is pulling the knee out of the trochlear groove
- Tibial tubercle transfer—realignment of the kneecap (usually an open procedure, not arthroscopic)