Soreness in the back of the thighs may be caused by fatigue injury of the muscles, or it may be caused by herniated lumbar discs and lactic acid buildup, and the ways to relieve it include physical therapy and medication. 1. Muscle fatigue injury: Excessive movement of the thighs may lead to muscle fatigue injury causing the symptoms of soreness on the back of the thighs. It is recommended to reduce or stop activities, take more rest and drink more hot water to promote the body’s metabolism. In the acute stage, patients can use cold compresses and elevate the affected limbs to avoid the aggravation of edema, etc. In the relief stage after 72 hours, they can take hot baths, massage and magnetic therapy. 2. Lumbar disc herniation: Lumbar disc herniation may cause soreness and pain on the back of the thigh due to the protruding nucleus pulposus compressing and stimulating the nerve root. It is recommended to carry out physical therapy at the same time, you can also carry out rehabilitation training to strengthen the strength of the lumbar back muscles, such as small swallow fly, hip bridge, etc.. Medication, such as oral celecoxib, can also be administered to relieve pain. Oral vitamin B1, methylcobalamin and other drugs to nourish peripheral nerves. 3. Lactic acid accumulation: because of excessive labor or excessive exercise, exertion, resulting in poor local blood circulation in the thighs, poor venous return, excessive accumulation of lactic acid, resulting in thigh pain. You should rest in bed, elevate the affected limbs, local physical therapy and cold compresses, hot compresses and other treatments can relieve it after 72 hours. If the patient’s symptoms of soreness on the back of the thigh are serious, or if the symptoms persist without improvement, he should go to the hospital for treatment. All of the above medications should be used under the guidance of a doctor, avoid self-medication.