Hamstring. (from WiThe biceps femoris is a muscle of the posterior (the back) thigh. As its name implies, it has two parts, one of which (the long head) forms part of the hamstrings muscle group.one, the long head, arises from the lower and inner impression on the back part of the tuberosity of the ischium, by a tendon common to it and the semitendinosus, and from the lower part of the sacrotuberous ligament.
Hamstring Tendonitis. The biceps femoris muscle runs from the back of the pelvis to the head of the fibula bone at the back of the knee laterally. If the tendon of the muscle at the knee insertion is partially torn it will become inflamed and cause pain (tendonitis). See: http://www.kneepain.co.uk/further-information/biceps-femoris-tendonitis for a more in depth description.