Hamstring group involves: the biceps femoris, the semimembranosus and the semitendinosus and connects two joints: hip and knee. Possible injury can involve strain or avulsion (tearing away) from the bone (rarely). Muscle strain is the tearing a few muscle fibers away and it involves usually the long head of the biceps femoris. Predisposed factors to injury are: poor blood circulation, poor flexibility, too weak warm-up, fatigue and imbalance between quadriceps femoris and hamstring muscles. It is common in sports, which require reflex, agility and fast acceleration (e.g. American football, rugby, football/soccer).
Avulsion is connected with hamstring tendon and usually occurs near ischium attachment. Pathomechanism is based on external force, which is toward leg flexion with knee extension maintaining, what is common in contact sports.
