Flesh pain on the thighs may be physiological reasons caused by lactic acid accumulation, or it may be caused by pathological factors such as muscle strain, pear-shaped muscle syndrome, and lumbar diseases. 1. Physiological reasons: the thigh has rich muscle tissue, long standing and sitting, long time large amount of physical activity, may cause fatigue or anaerobic metabolism of the thigh muscles, lactic acid and other metabolites of the accumulation, causing pain symptoms. 2. Pathological factors: if the warm-up before exercise is not sufficient, the muscles are suddenly exerted, which may cause the tearing of thigh muscle fibers and the above symptoms. The nerves innervating the thigh area are the sciatic nerve and its branches, if the sciatic nerve is compressed or overstimulated, the symptom of pain in the upper thigh may also occur, which may be caused by the damage of the pyriformis muscle in the area where the sciatic nerve passes out, such as the pyriformis syndrome. It may also be caused by lumbar diseases such as lumbar disc herniation, herniated nucleus pulposus or intervertebral disc compression of the peripheral nerve roots, causing pain in the thighs, which may also be accompanied by numbness, sensory abnormalities and other symptoms. If the symptoms of thigh pain are not relieved, or accompanied by other symptoms, you should go to the hospital in time to clarify the cause and give targeted treatment.