One leg is thin and the other is thick, generally considered to be caused by physiological factors and pathological factors, the specific causes need to be confirmed by the hospital examination. 1. Physiological factors Some people have unhealthy living habits or unhealthy sports, often only exercise one side of the leg, there will be a thin leg and a thick leg phenomenon, but there is no other abnormalities in the body, it is a normal phenomenon. 2. Pathological factors (1) Trauma: after the patient’s leg is fractured by trauma, if the patient uses plaster to fix it for a long time, due to the lack of exercise, one leg will be thin and one leg will be thick after removing the plaster. (2) Lower extremity venous thrombosis: If the patient suffers from lower extremity venous thrombosis, the blood return is not smooth, and the symptoms of one leg thin and one leg thick will appear. (3) Malignant lymphoma: malignant lymphoma will block the blood vessels, if the veins of the lower limbs are blocked and blood vessels are formed, one leg will be thin and one leg will be thick. If physiological factors are excluded, it is recommended to go to the hospital in time to clarify the cause of the disease and follow the doctor’s instructions for treatment.