Patellar dislocation is relatively common, especially in women, and patients complain of experiencing dislocation. A 30-degree CT of the knee joint can show the alignment of the patellofemoral joint. During the examination, the doctor pushes the patella outward with his hand, and the patient feels scared and refuses to continue the examination, which is medically called a positive fear sign and can confirm the diagnosis. The common cause of patellar dislocation is patellofemoral dysplasia, which occurs when the patella is dislocated to the outside under the action of a slight external force. The normal patella has four groups of soft tissue structures around the patella, which are arranged crosswise to hold the patella effectively in front of the knee joint, as shown. These structures limit the trajectory of the patella during knee flexion and extension activities. If these structures are defective, dislocation of the patella can result. As a result of patellar instability, patients often experience joint pain and instability, impingement and damage to the articular cartilage. Treatment requires surgical correction to prevent the patella from re-dislocating and causing damage to the articular cartilage and ligaments. Many patients ask if conservative treatment is possible, but it is generally ineffective, and as long as the joint is flexed and moved, or if there is minor trauma, there is a risk of re-dislocation, falls, and other injuries. Therefore, early surgical treatment is necessary.