Patellofemoral Pain Syndrome
Patellofemoral Pain Syndrome (PPS) is a common condition characterized by pain in the front of the knee, often linked to wear and stress on the knee joint. The term "patellofemoral" refers to the interaction between the patella (kneecap) and the femur (thigh bone). This syndrome can occur in one or both knees and is commonly associated with activities such as running, jumping, cycling, and even prolonged sitting. Symptoms may include not just pain, but also popping or cracking sounds from the knee, and in severe cases, the knee may give way. Diagnosis typically involves a manual examination, with imaging tests like X-rays or MRIs used selectively to rule out other conditions. Treatment often focuses on physical therapy to strengthen the quadriceps muscles, manage pain with ice or anti-inflammatory medications, and adjust activity levels to prevent exacerbation. Additionally, proper footwear and exercise modifications can help mitigate symptoms. While alternative treatments exist, their efficacy is not widely supported by scientific evidence, making ongoing research in this area important for understanding and managing PPS.
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Patellofemoral Pain Syndrome
Patellofemoral pain syndrome (PPS) is pain occurring in the front of the human knee, often due to wear and stress. The term patella is the kneecap, the bone cap of the knee joint, and femoral refers to the femur, or thigh bone. The patellofemoral joint is one of the two joints of the human knee, the other being the tibiofemoral. The syndrome can appear in one knee or in both knees. It is one of the most common injuries caused by running. Patellofemoral pain syndrome is also known as "runner’s knee" or "jumper’s knee," although it can occur in nonrunners as well, and "anterior knee pain syndrome." It is not caused by a specific disease or condition. In addition to pain, another occasional symptom of PPS is popping or cracking sounds from the knee. In extreme cases, the knee may give way.
Diagnosis is usually by manual examination. X-Rays or MRIs are generally not considered necessary for a diagnosis of PPS, although in some cases they may be used to rule out other explanations for the pain, such as arthritis in patients over fifty years old or a dislocated patella or other injury. Patellofemoral pain syndrome is also distinguished from bursitis of the knee, which also causes pain in the area of the patella but has a completely different physical cause. Chrondomalacia patellae is sometimes treated as a synonym for PPS, but it can be distinguished as a syndrome specifically caused by the degeneration of cartilage of the knee joint.
Background
Repetitive exercise straining the knee can be one cause of PPS in addition to running and jumping, cycling, climbing stairs, and squatting. The onset of PPS is often associated with a change in exercise routine such as the addition of a new exercise that puts pressure on the knee joint. Patellofemoral pain syndrome is frequently encountered by specialists in sports medicine. However, exercise or other physical activity is not necessary for PPS, and it can also appear in sedentary people. Weakness or inflexibility of the quadriceps muscles in the thigh can cause PPS. Women are particularly vulnerable to PPS, as well as to other injuries of the knee, due to the slight incurve of a woman’s hip bone, which increases the stress on the knee joint. Patellofemoral pain is often intermittent. It can appear during exercise or exertion, in extreme cases making exercise impossible, but it can also appear when going up or down stairs or after sitting for a long time in one position with the knee bent, as at a desk or at a movie or theater. Pain is often difficult for patients to localize.
One cause of PPS is poor tracking of the patella along the femur when the knee is bent, which in turn irritates the cartilage where the patella grinds against the femur rather than moving straight up and down. A slight misalignment of the patella aggravated by stress or repeated impact may lead to PPS. This may be caused by exercise or exertion with flat feet or poorly fitted shoes that increase the pronation, or rolling, of the foot which again puts strain on the knee.
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To prevent PPS, some doctors recommend exercises to increase the flexibility and strength of the quadriceps. Runners should avoid very hard surfaces and only gradually add uphill running to their routines. Properly fitting shoes are also valuable in preventing PPS. Theater-goers can try to get aisle seats, so they have room to occasionally straighten their legs.
Once patellofemoral pain strikes, immediate treatments to reduce it include ice packs. Antiinflammatory drugs and acetaminophen are also used to soothe the pain, although they have little effect beyond a few hours. Long-term treatments for PPS are based on physical therapy and are successful in over half of all cases. They include strengthening of the quadriceps muscles to restore muscle balance, as well as restricting those activities which cause pain. Hip strengthening has also been shown to be of some effectiveness. Knee braces which restrict the knee’s range of motion may be helpful, although the clinical evidence for this is weak. Evidence for the benefits of patellar taping, another commonly used treatment, is also weak. There are a very few extreme cases for which surgery is recommended.
If PPS is caused by exercise, some doctors recommend changing or minimizing exercise routines, particularly switching to activities that place less impact on the knee, such as swimming or cycling, as well as ensuring that the shoes used for exercise fit properly. Exercises involving squatting, such as burpees, are particularly aggravating and may need to be suspended. Practitioners of various alternative medicine techniques such as acupuncture, chiropractic, and Pilates claim the ability to treat PPS, but such claims are not backed by scientific evidence.
PPS is an active area of medical research. Research into PPS and other forms of anterior knee pain is funded by the Patellofemoral Foundation, a nonprofit organization founded in 2002 and headquartered in Farmington, Connecticut. The organization cosponsors an annual award for excellence in patellofemoral research along with the International Society of Arthroscopy, Knee Surgery and Orthopedic Sports Medicine and promotes knowledge of the patellofemoral joint among physicians and surgeons. There is also a biannual series of "Patellofemoral Pain Research Retreats and Clinical Symposia" held for physicians and other clinicians dealing with the problem.
Bibliography
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