Traumatic medial dislocation of the patella is an extremely rare injury and moreover its association with rotational malalignment along its longitudinal axis seems to be not reported. I had experienced a very rare injury of the patella that had been dislocated medially outside the medial femoral condyle with osteochondral fracture fragments at the lateral margin of the patella and 90°degrees clock-wise rotation along its longitudinal axis. So its articular surface faced medially. I tried several times of closed reductions, but in vain and had got a satisfactory result of painfree full recovery of the joint motion after open reduction and 4 weeks' long leg cast immobilization.