Extra-articular patellar dislocation with vertical axis rotation.

Extra-articular vertical dislocation is very rare. It occurs when the patella is forced crossing the lateral femoral trochlear surface, and rotated simultaneously along its longitudinal axis at about 90°, resulting in a wedged dislocation against lateral condyle. Reduction has been reported to require general anesthesia and an open procedure. We report a 19-year-old boy with extra-articular patellar dislocation, and a successful reduction was done by manipulation under local anesthesia. We believe that the mechanism of lateral vertical dislocation is the fulcrum mechanism.