I. Mechanism

  1. Imbalance between vastus medialis and lateral forces

II. Technique

  1. Knee exposed for observation
  2. Positioning
    1. Performs a single leg squat and stand or
    2. Lies supine with knee extended from flexed position

III. Interpretation: J-Sign

  1. Patella abruptly deviates medially on early flexion

Images: Related links to external sites (from Google)