The presence of patellofemoral pain is identified by anamnesis and physical examination performed by knee surgeons with more than 10 years' experience. The presence of all of the following criteria is required for diagnosis: typical complaint of anterior knee pain with a duration longer than 3 months (when going up or down stairs, squatting, remaining for long periods with bent knees), pain on palpation of the patellar articular surface and pain on patellar compression (reproducing the patient's complaint).