There are many reasons why the left calf is thicker than the right calf, the common ones are varicose veins of the left lower limb, right muscle wasting muscular dystrophy, poliomyelitis and so on. 1. Varicose veins of the lower limbs: blood stagnation in the veins of the left lower limb, weak walls of the veins and other factors may lead to venous tortuosity and dilatation. With the aggravation of the condition, heaviness, soreness and discomfort of the lower limbs may gradually appear, and some of them may have edema of the lower limbs. At this time, the left calf is thicker than the right calf. 2. Wasting muscle atrophy: if the limb activity is limited due to right calf fracture, the lack of muscle exercise for a long time can lead to muscle atrophy of the right calf, and the left calf is thicker than the right calf. 3. Poliomyelitis: a disease caused by poliovirus, can violate the nervous system, if the nervous system is severely damaged can appear paralyzed symptoms, paralyzed muscle groups occurring in the lower limbs of the unilateral, if it occurs in the right side, but also muscle atrophy, limb deformities, and so on. The left calf is thicker than the right calf may have other reasons, found abnormalities should be timely medical treatment, active standardized treatment, to avoid delaying the condition.