Which hamstring muscle internally rotates a flexed knee?

Which hamstring muscle internally rotates a flexed knee?

• A. Biceps femoris
• B. Semimembranosus
• C. Rectus femoris
• D. Semitendinosus

Answer: (D)

Internal rotation of a flexed knee is produced by the medial hamstrings as the tibia is pulled inward when the knee is bent. The semitendinosus is one of these medial hamstrings, crossing the knee on the inner side and helping rotate the tibia toward the midline while the knee is flexed. The other options don’t fit this action: the biceps femoris on the outer thigh tends to rotate the tibia outward when the knee is bent, and the rectus femoris is a quadriceps muscle whose main job is extending the knee (not rotating it). So the muscle that best fits this movement is the semitendinosus.

Internal rotation of a flexed knee is produced by the medial hamstrings as the tibia is pulled inward when the knee is bent. The semitendinosus is one of these medial hamstrings, crossing the knee on the inner side and helping rotate the tibia toward the midline while the knee is flexed. The other options don’t fit this action: the biceps femoris on the outer thigh tends to rotate the tibia outward when the knee is bent, and the rectus femoris is a quadriceps muscle whose main job is extending the knee (not rotating it). So the muscle that best fits this movement is the semitendinosus.