There are more classifications of patellar dislocation, as follows: 1. 4, fixed patellar dislocation, some people put fixed patellar dislocation and congenital patellar dislocation into one category, that is, regardless of flexion and extension, the patella is always dislocated outside; 5, recurrent patellar dislocation, recurrent patellar dislocation is actually the most common dislocation in clinical adolescents, in extension the patella is dislocated, and in 30° flexion the patella is reset into the pulley In extension, the patella is dislocated, and in 30° flexion, the patella is repositioned into the pulley, and in deep flexion, the patella is repositioned. There are other classifications of patellar dislocation, and the clinical treatment of different types of patellar dislocation is completely different, and the surgical approach is also different, and the prognosis is also different.