Semitendinosus: Origin/proximal attachment: the ischial tuberosity, aka - the "sit bone". Insertion/distal attachment: upper part of the tibia near the tibial tuberosity - an area known as the pes anserine. Semimembranosus: Origin/proximal attachment: ischial tuberosity, aka - the "sit bone". Insertion/distal attachment: the back of the inside top part of the tibia (posterior medial condyle of the tibia). Biceps femoris: Origin/proximal attachment: Long head - ischial tuberosity, aka - the "sit bone" Short head - bottom part of the femur next to a raised line called the linea aspera. Insertion/distal attachment: outside of the head (top) of the fibula.