Criteria for diagnosis – all 3 of the following
(1) appropriate history and clinical history
(2) appropriate findings on physical examination
(3) exclusion of other causes such as patella fracture or traumatic dislocations
Additional findings:
(1) age of the patient usually is from 12 – 35 years (adolescent and early adult)
(2) pain usually relieved by rest or application of ice
Appropriate history and clinical history involves all of the following:
(1) history of insidious onset of anterior knee pain
(2) retropatellar or peripatellar pain
(3) pain exacerbated by jumping OR ascending stairs OR descending stairs
(4) positive theater sign (worsening of pain with prolonged sitting, relieved by straightening the knee)
(5) history of crepitus
Appropriate findings on clinical examination - both of the following:
(1) poorly developed vastus medialis obliquus
(2) 2 or more of the following:
(2a) increased Q angle (> 20 degrees)
(2b) excessive genu recuvatum (> 10 degrees of hyperextension)
(2c) patella alta
(2d) femoral anteversion
(2e) external tibial torsion
(2f) hamstring muscle contracture
(2g) positive Clarke sign (pain elicited when the examiner presses the patella against the femur during quadriceps contraction with the knee fully extended)
(2h) tenderness of the medial or lateral patellar facet
where:
• Joint crepitus involves a grating sensation as the knee is flexed and extended.
• The Q angle is the angle between:
(a) The line drawn from the anterior superior iliac spine to the midpoint of the anterior patella surface.
(b) a line through the midpoint of the anterior patella surface, tibial tuberosity and midline of the tibia
• Patella alta: The patella rests precariously on the anterior femoral surface proximal to the stabilizing trochlear groove (Minkoff and Simonson).
