Soreness in the left buttock and left thigh is commonly caused by lumbar disc herniation and pear-shaped muscle syndrome, as follows: First, lumbar disc herniation: patients with lumbar disc herniation can first show symptoms of soreness in the left buttock and left thigh, while lumbar pain is not obvious, and with the continuous development of the disease, there will also be lumbar pain with limited lumbar spine activities. Patients can find herniated nucleus pulposus nerve compression by CT scan or MRI of lumbar spine. Second, pear-shaped muscle syndrome: spasm, tension or scar formation of the pear-shaped muscle can compress and stimulate the sciatic nerve, causing the symptoms of left hip and left thigh pain, accompanied by weakness of the left lower limb. Patients can clarify the sciatic nerve lesion and its severity through electromyography examination. Patients with the above symptoms can obtain satisfactory relief with early diagnosis and early treatment. If the condition is delayed, it can result in serious consequences such as muscle atrophy of the left lower limb.