Table 1.

Inclusion and Exclusion Criteria

Criteria
Inclusion
Nontraumatic peripatellar or retropatellar pain >3 mo
Worst pain over last week >3/10 assessed by visual analog scale
Pain with ≥2 of the following activities:
Stair ambulation
Running
Jumping
Prolonged sitting
Quadriceps contraction
Kneeling
Pressure over the patella
Exclusion
Previous knee surgery
Ligamentous instability defined by orthopaedic special tests (anterior  and posterior drawer, valgus and varus stress test)
Additional source of anterior knee pain (eg, tendinitis, bursitis,  patellar subluxation)
Lower extremity or back injury or concussion in the year before the  study