Patellofemoral pain syndrome

Lore & Background

Patellofemoral pain syndrome typically has a gradual onset, though some cases appear suddenly after trauma. The pain is diffuse and vague around or behind the kneecap, often described by patients as a circle around the patella—the 'circle sign.' Pain is triggered by activities such as ascending or descending stairs, squatting, kneeling, cycling, or running, and prolonged sitting with a bent knee can cause discomfort, sometimes called the 'movie sign' or 'theatre sign.' The pain is usually aching and occasionally sharp, and the knee may click, though this is unrelated to pain or function.

Reader's Guide

Patellofemoral pain syndrome is significant as the most prevalent cause of knee pain, affecting a large proportion of young adults and athletes, especially runners. Its diagnosis relies primarily on symptoms and physical examination, with tests like pushing the kneecap into the femur increasing pain suggesting the condition. Treatment typically involves rest and rehabilitation with a physical therapist, with exercise therapy being the recommended first line. Runners may need to switch to activities like cycling or swimming, and insoles may help some people. Despite treatment, symptoms may last for years. The condition highlights the importance of addressing muscle imbalances, particularly quadriceps weakness, and proximal factors such as hip strength. The exact cause remains unclear, but overuse, trauma, increased training, and weak quadriceps are risk factors. The syndrome is distinguished from chondromalacia patellae, though in practice the difference is often theoretical due to lack of routine imaging.

Did You Know?

• Patellofemoral pain syndrome is the most common cause of knee pain, affecting more than 20% of young adults.
• It occurs about 2.5 times more often in females than males.
• Pain during prolonged sitting is sometimes called the 'movie sign' or 'theatre sign.'
• The condition is particularly common among runners.