Gastrocnemius- Notice the bones view on the left, and how the Femur (thigh bone) meets the Tibia and Fibula (Shin bones) to form the knee joint. Now, look at the image on the right showing the connection of the Gastrocnemius to the Femur crossing the knee joint and connection to the Femoral Condyles. Because of the crossing connection, the Gastrocnemius aids the hamstrings with flexion of the knee.