The most common causes of short and long legs are physiological factors, trauma, developmental abnormalities, necrosis of the femoral head, etc. If the patient is accompanied by obvious symptoms of discomfort, it is recommended to consult a doctor in time for treatment. 1. Physiological factors: Generally speaking, the length of the left and right legs of some people is different, usually within 2 centimeters, which is a relatively normal physiological difference, and there is no uncomfortable symptoms, and it is difficult to find abnormalities in appearance. 2. Trauma: Improper treatment of fractures and deformed healing can easily cause the length of the left and right lower limbs to be different. 3. Developmental abnormality: some people will have congenital hip deformity and dysplasia, which will lead to short and long legs. 4. Necrosis of the femoral head: ischemic necrosis of the femoral head will eventually cause wear and absorption of the femoral head, and the bony structure is abnormal, which will easily lead to the difference in the length of the left and right legs. The causes of short and long legs are many, and may also be related to polio, hemiplegia, etc. It is recommended to go to the hospital in time to find out the cause of the disease and carry out targeted treatment.