The onset of the condition is usually gradual, although some cases may appear suddenly following trauma. The most common symptom is diffuse vague<unk>  around the kneecap (peripatellar) and localized<unk>  focused behind the kneecap (retropatellar). Affected individuals typically have difficulty describing the location of the<unk> . They may place their hands over the anterior patella or describe a circle around the patella. This is often called the "circle sign".<unk>  is usually initiated when weight is put on the knee extensor mechanism, such as when ascending or descending stairs or slopes, squatting, kneeling, cycling, or running.<unk>  during prolonged sitting is sometimes termed the "movie sign" or "theatre sign" because individuals might experience<unk>  while sitting to watch a film or similar activity. The<unk>  is typically aching and occasionally sharp.<unk>  may be exacerbated by activities. The knee joint may exhibit noises such as clicking. However, this has no relation to<unk>  and function. Giving-way of the knee may be reported. Reduced knee flexion may be experienced during activities.
Patellofemoral pain syndrome
Chondromalacia patellae
Patellar subluxation syndrome
Patellar tendinitis
Greater trochanteric pain syndrome
Infrapatellar fat pad syndrome
Anterior compartment syndrome
Infrapatellar bursitis