There are many reasons for the soreness of the lower hip and the back of the thigh, both physiological and pathological. Physiological is mainly due to muscle damage caused by excessive exercise and overly violent stretching movements, and this symptom can be relieved by resting for a period of time. Most of the patients’ symptoms are aggravated after bending and straining, and can be relieved after rest. 3. Infrequent exercisers can also suffer from soreness under the hip and rear of the leg due to lactic acid accumulation, soft tissue damage to the muscles and inflammatory stimulation after strenuous activities.