Hamstring muscle injury is characterized by reddening of the skin, swelling, pain, and limitation of activities, and if the symptoms persist, it is recommended to seek medical attention in time. 1. Reddening of the skin: Hamstring muscle is the general name of the muscle group of the back side of the thigh, which includes semitendinosus, semimembranosus and biceps femoris, if the hamstring muscle is damaged, the local skin will appear red and hot. 2. Swelling: if there is an inflammatory reaction after hamstring muscle injury, swelling of the back side of the thigh is easy to appear. 3. Pain: the more typical feature is pain in the posterior thigh, which may be aggravated when pressed. 4. Limitation of activities: hip joint cannot be fully extended, hip flexion is limited, gait swing phase elevation ability is reduced, or limp, may also be accompanied by a decrease in muscle strength, muscle atrophy, flexion of the knee and the knee’s rotation in and out of the limitation. If popliteal muscle injury occurs the above performance, it is recommended to go to the hospital in time for examination, targeted treatment by the doctor, usually pay attention to the protection of thigh muscles, reduce strenuous exercise.