The patella is an important factor in maintaining knee joint stability and knee extension strength, and it prevents anterior-posterior misalignment and excessive internal and external rotation between the tibia and femur in the semi-flexed knee position. Patellar dislocation can be divided into two categories: direct external force and indirect external force, such as kneeling, kicking and hitting the patella of the knee. Indirect external forces such as knee torsion, knee inversion and valgus can also cause patellar dislocation. Sometimes patellar dislocation is related to anatomical abnormalities, such as high patella, joint laxity, knee valgus, knee hyperextension, femoral epicondyle hypoplasia and quadriceps medial head dysplasia. The other condition is patellar subluxation. Patellar subluxation is actually just an abnormal relationship between the patella and the femoral pulley surface, not a complete dislocation of the patella to the pulley surface, but also a legacy of complete dislocation after reset. The clinical discomfort of patients with patellar subluxation is often dominated by patellofemoral arthropathy, and a few people will have the feeling of frequent minor sprains of the knee joint, or feel the patella shake a little when the knee joint is sprained. Because knee injuries caused by patellar subluxation are generally mild, swelling and pain in the knee joint can quickly disappear or be cured. Each episode of complete patellar dislocation is characterized by severe knee swelling and pain. Both patellar subluxation and patellar dislocation can lead to fear of reoccurrence because of repeated episodes and recurrent patellofemoral joint symptoms and discomfort. In the treatment of the first acute injury that caused the patellar subluxation or dislocation, conservative treatment may be considered. Conservative treatment consists of manual repositioning, joint cavity aspiration to remove the intra-articular blood collection, and compression bandaging and braking of the affected knee for three weeks. Surgical treatment can be performed for acute injuries or after conservative treatment has failed. During surgery, if the patellar dislocation or subluxation is caused only by a tear of the medial patellofemoral ligament and the medial patellofemoral support ligament, only the medial patellofemoral support ligament and medial patellofemoral ligament repair is performed. If the injury is combined with avulsion fracture of the medial patellar rim or osteochondral fracture, surgical excision of the fracture fragment followed by suture repair of the supporting band and medial patellofemoral ligament is indicated. For recurrent or habitual patellar dislocation and subluxation, different surgical approaches are taken depending on the case. For example, the lateral patellar support band is released, the medial head of the quadriceps muscle is inferiorly displaced, the medial patellar support band is tightened, and the tibial tuberosity is inferiorly displaced. Surgical correction is also required for severe knee valgus or inversion deformities.