Semitendinosus action includes which of the following?

• A. Flex the knee, medially rotate the flexed knee, extend the hip, medially rotate the hip, tilt pelvis posteriorly
• B. Flex the knee, laterally rotate the knee, extend the hip, laterally rotate the hip
• C. Extend the knee, medially rotate the hip
• D. Flex the knee, medially rotate the hip, extend the knee

Answer: (A)

The semitendinosus is a two‑joint muscle of the posterior thigh that crosses both the hip and knee. Its actions reflect that dual role: it helps bend the knee and, when the knee is flexed, it tends to rotate the tibia inward (medial rotation). At the same time, because it crosses the hip posteriorly, contracting it assists in extending the hip. This same muscle can contribute to a medial rotation of the thigh when the hip is flexed and tends to tilt the pelvis backward (posterior tilt) with its pull on the pelvis and thigh.

So the sequence of actions—flex the knee, medial rotation of the flexed knee, extend the hip, and assist in medial rotation of the hip along with posterior pelvic tilt—fits the known behavior of the semitendinosus. The other described movements (lateral rotation of either the knee or hip, or knee extension) don’t align with how this muscle functions.