If you have soreness under your buttocks or on the back of your thighs, first of all, consider that it is caused by overexertion, so you should pay more attention to rest and sleep on a hard bed. Secondly, it is considered to be caused by local pressure, such as sleeping in one position or repeating one action for a long time. Pay attention to the movement of the limbs to avoid local compression, you can use hot towels on the back of the thigh for hot compresses. If the pain is severe, you can also take drugs with anti-inflammatory and analgesic effects such as diclofenac, and you can also use drugs for muscle spasm such as eperisone hydrochloride. Finally, sodium bicarbonate can also be taken to improve the local acidic environment. Besides, pathological causes should be considered, such as lumbar disc herniation, femoral head necrosis, rheumatoid arthritis, etc., which require further clear diagnosis in hospital.