The semitendinosus originates from the ischium (hip). Its long, narrow, fleshy belly ends two-thirds of the way down the thigh at its tendon. It sits in the muscular groove formed in the semimembranosus muscle at the inner back of the thigh. This muscle flexes the lower leg and extends the thigh at the hip joint. It is considered one of the hamstring muscles. Its tendon, along with the tendons of the semimembranosus and the gracilis, form the inner hamstring.
