The thickening of one side of the calf after injury and the thinning of the uninjured one may be caused by ageing, soft tissue damage to the injured leg, and prolonged bed rest. 1. Ageing: With age, the muscle content of the human body gradually decreases, resulting in the thinning of the uninjured leg. At the same time, the blood circulation of the injured leg slows down, swelling occurs, and the phenomenon of thickening occurs. 2. Soft tissue injury of the injured leg: when the calf is injured, the local muscles, ligaments, fascia and other soft tissues of the calf become congested, edema and other aseptic inflammation, thus causing swelling of the injured calf. The uninjured calf is affected by the affected side, the movement is reduced, muscle nutrition, blood supply is reduced and the symptoms of thinning appear. 3. Prolonged bed rest: lying in bed without movement after a calf injury can lead to poor blood circulation in the injured calf and cause swelling and thickening. At this time, it will also make the uninjured calf muscle nutrient deficiency and cause the symptoms of thinning. In short, there are many reasons why the injured calf becomes thicker and the uninjured calf becomes thinner, so it is recommended to go to the hospital for a comprehensive examination to clarify the diagnosis and targeted treatment.