1.Why is the patella dislocated? The patella is an important structure for maintaining knee joint stability and knee extension strength. When we put our hands on the front of the knee joint, the round hard structure we feel is the patella, and during knee flexion, the groove structure formed by the patella and the slide and the support band on both sides of the patella (similar to the reins on both sides of the horse’s head) prevent the patella from dislocating to the side. Once this balance is disturbed, it can lead to patellar dislocation. Direct external forces such as kneeling, kicking or hitting the patellar part of the knee, or indirect external forces such as knee torsion, internal or external knee rotation can cause patellar dislocation. Another 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 femoral pulley surface, but also a complete dislocation left after the reset. 2.How should patellar dislocation be treated? For patients with first-time patellar dislocation, conservative treatment can be considered in the acute phase. The conservative treatment includes: manual repositioning, compression bandaging (not too tight), fixation of the knee in the straight position for three weeks, followed by knee flexion exercises. However, even after strict conservative treatment there is a high rate of recurrence. In recent years, it has also been suggested that if surgical treatment, i.e., suturing of the torn support band, is taken in the acute phase, the recurrence rate is lower and the outcome is better after surgery. Repeated patellar dislocation caused by repeated sprains is called recurrent patellar dislocation, while patellar dislocation that comes out on its own every time the knee is flexed is called habitual patellar dislocation, and recurrent and habitual dislocations require surgical treatment. There are many surgical treatment methods for patellar dislocation, the common ones are internal inferior displacement of the medial head of the quadriceps and internal inferior displacement of the attachment point of the patellar tendon of the tibial tuberosity, etc. These traditional procedures are generally more thorough in correcting the dislocation, but they are often traumatic and slow to recover. With the development of minimally invasive joint surgery, some minimally invasive treatment methods have also achieved better results. For some patients with moderate or mild dislocations, if the anatomical variation is not significant, the use of arthroscopic tightening and suturing or reconstruction of the medial patellar support band combined with the release of the lateral support band has also achieved good results, and the recovery is faster and the skin incision is more beautiful. For habitual or severe recurrent dislocations, a combination of support band reconstruction and osteotomy is usually required, which results in a slower recovery and poorer outcome compared to mild to moderate lesions.