A hamstring injury is an injury to the muscles in the back of the thigh. The hamstrings, which straighten the hip and bend the knee, are weaker than the opposing quadriceps muscles, at the front of your thigh. If the hamstrings are not at least 60% as strong as the quadriceps, the quadriceps overpower and injure the hamstrings. Immediate treatment includes; R.I.C.E. therapy: Rest, Ice, Compression (adhesive strapping), and Elevation. Then after healing begins, stretch and strengthening exercises can prevent re-injury.