The causes of thigh soreness may include fatigue, calcium deficiency, pyriformis syndrome and lumbar disc herniation. 1. Fatigue: After strenuous exercise and long-time physical labor, lactic acid accumulates in the thigh muscles, which can cause thigh soreness and pain, which is a normal phenomenon, so you can rest and reduce activities. 2. Calcium deficiency: If the calcium absorption ability of the elderly or partial food decreases, resulting in calcium deficiency, thigh soreness may also occur. 3. Piriformis syndrome: due to improper posture, trauma and other reasons, causing the piriformis muscle tension spasm after the sciatic nerve pressure, can also appear thigh pain, mostly accompanied by pain in the buttocks. 4. Lumbar disc herniation: lumbar disc degeneration and protrusion, compression to the nerve root, thus causing thigh pain, mostly accompanied by lumbar pain and discomfort. Causes of thigh soreness are many, and may also be related to cold, bacterial infection, trauma, lower extremity vascular disease, etc. If the symptoms continue to be unrelieved, it is recommended to consult a doctor in a timely manner, under the guidance of the doctor’s diagnosis and treatment.