The knee, also known as the patella, wobbles loosely from side to side can be caused by patellar dislocation, laxity of the patellar ligament, and so on. In normal people, the patella can move up and down or left and right, but the movement is generally small, especially the left and right movement is much smaller than the up and down movement. Only when the knee joint is straight or over-extended, the quadriceps muscle relaxes, and then the patella can move slightly left and right. 1. Patellar dislocation: when the knee is flexed and the patella is able to move widely, especially left and right, then it is very likely that the patella is dislocated, usually due to violence and trauma. Treatment requires surgery to tighten the patellar ligament. 2. Patellar ligament laxity: usually seen as a sequela after some trauma. For such cases, the best treatment is surgery to be able to reset the patella. It is recommended that patients go to the hospital to do knee CT, MRI and other related examinations, in order to clarify the condition, and be treated by a professional physician, not blindly use their own medicine.