Patients with one thick leg and one thin leg can be seen in a variety of diseases, as follows: 1, thigh fracture: thigh fractures often require cast braking, during the braking period due to the reduction of limb activity, muscle atrophy will occur, so when the cast is removed, you can mostly observe the affected side of the leg thinner. 2, congenital hip dysplasia: due to the presence of pain in the affected side of the hip joint, patients often avoid using the affected hip, and Therefore, the muscles on the healthy side will be enlarged and thickened, while the muscles on the affected side will be atrophied, showing that one leg is thick and the other leg is thin. In addition, unilateral osteoarthritis can also be seen, with a similar mechanism of thick and thin changes, mainly due to the patient’s refusal to use the affected knee joint, while mainly using the healthy knee joint for compensatory activities, thus resulting in bilateral leg thickness inequality.