Patellar force imbalance may be caused by congenital factors such as abnormal development of soft tissues around the patella and abnormal patellar development, or by acquired factors such as knee deformity and trauma. 1. Congenital factors: Patellar force imbalance, clinically known as patellar instability. The main reason of patellar instability caused by congenital factors has a great relationship with the abnormal development of soft tissues around the patella, abnormal development of the patella and other structural abnormalities in the anterior knee area, such as femoral condylar dysplasia, abnormal development of the trolley, splitting the patella, abnormal patella, high patella and so on. 2. Acquired factors: Acquired trauma as well as inversion and eversion deformity of the knee joint may also cause patellar instability. Such as patellar fracture, patellar ligament rupture, medial supportive band rupture, cruciate ligament tear, osteoarthritis of the knee and so on. Acquired factors can cause abnormalities in the peripatellar structures, bilateral force imbalances, and patellar instability. Patellar force imbalance may also have other causes, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment or treatment under the guidance of the doctor.