The symptoms of patellar dislocation are different according to the classification, and the common symptoms are as follows: 1. Traumatic patellar dislocation: patellar dislocation caused by trauma, local pain and swelling are more obvious. After patellar dislocation, even if it does not return, there may be local deformities, skin petechiae, local bleeding spots, and limited flexion and extension activities; 2. Recurrent patellar dislocation: the main manifestation is that when the patient flexes and extends the joint, the patellar trajectory becomes abnormal, and the patient develops prepatellar pain, knee swelling, and weak legs when going up and down stairs or walking. If the patella is dislocated and the fracture fragments fall into the joint cavity, the patient may experience interlocking during walking, which means that the joint suddenly becomes stuck and cannot walk, with severe pain; 3. Fixed patellar dislocation or habitual patellar dislocation: the patella can be clearly felt outside of the carriage during clinical examination, in flexion and extension, especially in flexion, which is outside of the carriage track. However, the clinical examination may show a high patella and a positive patellar fear test, that is, when the patella is pushed gently to the outside and the knee joint is flexed, the patient will be afraid and painful; of course, some patients may also show signs such as knee valgus deformity, or tibial external rotation deformity. Based on the imaging examination, a clear diagnosis of patellar dislocation can usually be made and the correct treatment given.