The healing time for hamstring injuries varies greatly and depends on the severity of the injury, according to NHS Choices. If the hamstring is simply pulled or strained, it may heal completely in a few days. However, more serious injuries may take months to heal completely. In particularly severe cases, surgery may be necessary to repair the damage, extending the recovery time even more.
The hamstring is not one muscle. Instead, it is a combination of three different distinct muscles which all work together. The three muscles are the semitendinosus, the semimembranosus and the bicep femoris. The hamstring muscles allow the leg to move behind the body and they allow the knee to bend, according to the American Academy of Orthopaedic Surgeons. Injuries to the muscles are most common when the hamstring is stretched too far or is forced to accommodate a sudden, heavy load. Sports that feature a lot of sprinting, such as soccer, often cause hamstring injuries.
NHS Choices explains that there are three different grades for hamstring injuries. Grade 1 injuries involve slight pulls or strains. Grade 2 injuries feature a partial tear of one or more of the hamstring muscles. Grade 3 injuries, the most serious type, include complete tears of one or more of the muscles.