Ace the 2026 Gross Anatomy Challenge: Lower Body Mastery Awaits!

Semitendinosus is a hamstring that crosses both the hip and knee joints and inserts on the medial tibia. At the knee, when you flex the leg, this muscle pulls the tibia toward the midline and rotates it inward. So the action you feel is bending the knee with medial rotation of the tibia. That’s why the correct description is flexing the leg and medially rotating the tibia. It doesn’t primarily extend the thigh, abduct the thigh, or rotate the thigh laterally at the hip—those actions belong to other muscles.