Knowing how to recognize the most common signs of a hamstring injury, as well as the type of hamstring injury, is crucial to ensure that the appropriate medical care is received right away. The most common signs include: Sharp Pain — Often preceded by a “snapping” or “popping” sound at the moment of injury, hamstring tears typically cause a sharp pain in the back of the thigh or underneath the buttocks. Swelling and Bruising — Most people experience some swelling and bruising when they tear their hamstring as it causes significant tissue damage. While it might take a couple of days for bruises to become visible, swelling is often apparent within a few hours of the injury. Leg Weakness — Because the hamstrings are responsible for the movements of the hips and knees when walking, running, squatting, or bending, most people experience weakness in their legs during any of these movements after a hamstring injury. Problems Bearing Weight — In addition to weakness and swelling, a torn hamstring can make it difficult to bear weight on the affected leg. Weight-bearing can also cause significant pain.