Thick legs on one side and thin legs on the other side may be related to physiological factors, edema, muscle atrophy and other reasons. 1. Physiological factors: It may be that the exercise is not paid attention to the balanced exercise, resulting in one leg muscle is more developed than the other, appearing leg thick and thin. 2. Edema: It is common in deep vein thrombosis of the lower limbs, due to the blockage of veins by thrombus, resulting in poor blood flow and blood stagnation, which makes the affected side of the leg swollen, and the leg is thick and thin at the same time. 3. Muscle atrophy: This may be caused by herniated lumbar discs and other diseases, resulting in compression of the sciatic nerve and loss of muscle nutrients. The muscles of one side of the lower limb atrophy, and the leg is thick and thin at the same time. Thick legs on one side can also be seen in other causes, it is recommended to consult a doctor in a timely manner, follow the doctor’s instructions for relevant examinations, with the help of the doctor to clarify the cause, and targeted treatment or treatment.