<Li> Muscle will participate in flexion of the knee joint and extension of the hip joint . </Li> <P> Those muscle which fulfills all of the four criteria are called true hamstrings . The adductor magnus reaches only up to the adductor tubercle of the femur, but it is included amongst the hamstrings because the tibial collateral ligament of the knee joint morphologically is the degenerated tendon of this muscle . The ligament is attached to medial epicondyle, two millimeters from the adductor tubercle . </P> <P> The three muscles of the posterior thigh (semitendinosus, semimembranosus, biceps femoris long & short head) flex (bend) the knee, while all but the short head of biceps femoris extend (straighten) the hip . The three' true' hamstrings cross both the hip and the knee joint and are therefore involved in knee flexion and hip extension . The short head of the biceps femoris crosses only one joint (knee) and is therefore not involved in hip extension . With its divergent origin and innervation it is sometimes excluded from the' hamstring' characterization . </P> <Table> <Tr> <Td> Muscle </Td> <Td> Origin </Td> <Td> Insertion </Td> <Td> Nerve </Td> </Tr> <Tr> <Td> semitendinosus </Td> <Td> ischial tuberosity </Td> <Td> medial surface of tibia </Td> <Td> tibial part of sciatic </Td> </Tr> <Tr> <Td> semimembranosus </Td> <Td> ischial tuberosity </Td> <Td> medial tibial condyle </Td> <Td> tibial part of sciatic </Td> </Tr> <Tr> <Td> biceps femoris - long head </Td> <Td> ischial tuberosity </Td> <Td> lateral side of the head of the fibula </Td> <Td> tibial part of sciatic </Td> </Tr> <Tr> <Td> biceps femoris - short head </Td> <Td> linea aspera and lateral supracondylar line of femur </Td> <Td> lateral side of the head of the fibula (common tendon with the long head) </Td> <Td> common peroneal </Td> </Tr> </Table>

Where do the hamstrings originate as a group