Left leg calf numbness is commonly caused by lumbar diseases, pear-shaped muscle syndrome, etc., as follows: First, lumbar diseases: lumbar diseases such as lumbar disc herniation and lumbar spinal stenosis can compress the nerve roots in the lumbar region, causing sensory conduction dysfunction in the left lower limb, especially in the left calf. Patients will show symptoms of numbness in the lower leg, and will be accompanied by lumbar pain, lumbar spine activity restriction, and sometimes there can be radiated pain in the lower limbs, and the site of compression and the degree of compression can be confirmed by lumbar MRI scan. Second, pear-shaped muscle syndrome: spasm or scarring of the pear-shaped muscle can cause compression and stimulation of the sciatic nerve, resulting in numbness of the left calf. Electromyography examination of the lower limbs can reveal sciatic nerve conduction dysfunction, including both motor conduction and sensory conduction function. Patients presenting with numbness in the left calf should be seen and treated promptly to restore nerve conduction as soon as possible.