Traumatic patellar dislocation is mostly caused by the tearing of the medial patellar support band structure due to sudden large direct or indirect violence to the patella, because some patients can reset themselves, so it is easy to miss and misdiagnose. In the past, conservative treatment was the main treatment, but conservative treatment is often accompanied by significant laxity of the medial patellar support band after scar healing, and is prone to re-dislocation, with a recurrence rate of 17%-44%, and about half of the patients may experience re-dislocation or multiple dislocations within 2 years after the first dislocation. In patellar dislocation, the medial articular surface of the patella impinges on the femoral epicondyle, often resulting in damage to the articular cartilage surface and even the formation of a free body, so surgery is often advocated for patients with patellar dislocation. The stability of the patella is dependent on both the surrounding bone and soft tissue factors. When the knee is extended, the patella is detached from the femoral glide surface and relies on the soft tissues to maintain patellar stability. As the knee flexes to 15°-20°, the patella gradually enters the femoral glide and the medial patellofemoral ligament gradually relaxes, subsequently requiring the block of the femoral epicondyle to maintain patellofemoral stability. In recent years, with in-depth studies on biomechanics, it has been confirmed that the medial patellofemoral ligament is the most important static restraining structure to maintain patellar stability, and it provides 53% of the total restraining force of the medial patella. The medial patellofemoral ligament is tense in most cases when the knee is fully extended, and this is when the limiting force on the patella is strongest. Medial patellofemoral ligament injury is present in 95-100% of patients with recurrent patellar dislocation, so medial patellofemoral ligament laxity or injury is the primary pathologic anatomic basis for patellar dislocation. Under normal conditions, there is a lateral femoro-tibial angle of approximately 170° in the knee joint, and an outward angle between the quadriceps contraction line and the patellofemoral ligament line of force, the Q angle, which also results in an outward combined force during quadriceps contraction leading to a tendency for the patella to dislocate outward. Studies have shown that the Q angle is greatest at 30° of knee flexion, when the patella has not yet entered the femoral carriage and is in its most unstable state, and the role of the medial patellofemoral ligament is significantly weakened at this position, so the Q angle is too large to easily dislocate the patella laterally. Therefore, patients with an increased Q angle greater than 15° in men and greater than 20° in women require additional internal displacement of the tibial tuberosity at the patellar ligament stop. Further, the compressive stress between the patella and the femoral epicondyle increases in patients with increased Q angle, and there is mostly wear of the lateral articular surface of the patella and the lateral articular surface of the femoral talus. The wear of the articular cartilage surface is transferred arthroscopically through the tibial tuberosity, which helps to relieve the pressure on the patellofemoral joint and also allows the contact surface of the patellofemoral joint to change. The medial patellofemoral ligament is the main limiting structure of the patella and effectively antagonizes patellar outward migration until 30° of knee flexion. The ligament remains isometric from the fully extended knee position to the 70° flexed knee position. Therefore, when reconstructing the medial patellofemoral ligament for femoral end compression screw fixation, we flex the knee about 60 degrees and wait until the patella is fully in the glide before tensioning the graft, which can effectively prevent excessive tension on the graft. In reconstructive surgery of the medial patellofemoral ligament, the isometric properties of the graft are critical to the success of the surgery, and the positioning of the femoral stop of the medial patellofemoral ligament is the key to determining the isometric properties of the graft. When the femoral stop is too close, it will result in increased pressure between the medial patellar surface and the femur, while if it is too far away, it will cause excessive tension on the reconstructed ligament, resulting in the medial patellofemoral ligament failing to function physiologically. Medial patellofemoral ligament reconstruction is effective and safe in the treatment of traumatic patellar dislocation. The key factors for successful medial patellofemoral ligament reconstruction surgery are to correctly grasp the indications, comprehensively understand the interaction between the bony and soft tissue limiting structures of the patella, determine the need for simultaneous surgery of the distal lateral row of the medial support band according to the patient’s pathological changes, correctly select the position of the femoral and lateral patellar tunnels, and restore the normal patellofemoral joint alignment.