Trochlear dysplasia is most important risk factor for patellar instability. Imaging provides an objective basis for the morphological abnormalities of the trochlea, Existing dysplasia is classified based on imaging findings. The current techniques of trochlear osteotomy have been described to correct the bony anatomy and cartilage groove. Although it can be used as a salvage procedure after unsuccessful instability surgery, the ideal is to identify the deformity early and perform primary surgery. Although these techniques do not prevent the progression of patellofemoral arthritis.