Table 1 Inclusion and exclusion criteria^a

 1. Insidious onset of symptoms unrelated to trauma and persistent for at least 4 wk

 2. Pain in the anterior knee associated with at least 3 of the following:

  a. During or after activity (running and other physical activity modalities)

  b. Prolonged sitting

  c. Stair ascent or descent

  d. Squatting

 3. Pain with palpation of the patellar facets or pain during step down from a 20-cm box or during a double-legged squat

Exclusion criteria

 1. Meniscal or other intra-articular injury

 2. Cruciate or collateral ligament laxity or tenderness

 3. Positive patellar-apprehension sign

 4. Evidence of effusion

 5. History of recurrent patellar subluxation or dislocation

 6. History of surgery to the knee joint

 7. Nonsteroidal anti-inflammatory drug or corticosteroid use within 24 hours before testing

 8. History of head injury or vestibular disorder within the last 6 months

 9. Pregnancy