The J-sign is a clinical examination of the knee joint that if positive, often indicates lateral patellar tracking.
- Patient seated with knee bent 45°.
- Examiner instructs patient to straighten knee while observing patellar tracking
If the examiner observes patellar deviation laterally in the shape of the letter “J” with knee extension then this probably shows Patellar tracking dysfunction, vastus medialis oblique deficiency, or increased Q-angle.
Etiologies associated with patellofemoral disorders; vastusmedialis oblique deficiency, Q-angle, lateral retinacular tightness/plica, patella alta or baja, patellofemoral groove depth, abnormal patellar tracking.