Which muscles are active during non-weight-bearing medial rotation of a flexed leg?

Which muscles are active during non-weight-bearing medial rotation of a flexed leg?

• A. Popliteus; Semimembranosus; Semitendinosus; Sartorius; Gracilis
• B. Biceps Femoris; Rectus Femoris; Gastrocnemius
• C. Gastrocnemius; Plantaris; Tibialis Anterior
• D. Tensor Fasciae Latae; Gluteus Maximus

Answer: (C)

When the knee is flexed and not bearing weight, the leg can rotate internally around the knee joint. The muscles that actively produce this medial rotation are those that cross the knee and can pull the tibia toward the midline as the knee flexes. The gastrocnemius and plantaris cross the knee and, in a flexed, non‑weight‑bearing position, contribute an internal rotational component to the tibia as they help drive knee flexion. The tibialis anterior, while primarily acting on the ankle, also participates by stabilizing the leg and supporting the coordinated inward torque of the lower limb during this motion. This combination yields medial rotation of the tibia when the leg is flexed and the foot is not weight-bearing.

When the knee is flexed and not bearing weight, the leg can rotate internally around the knee joint. The muscles that actively produce this medial rotation are those that cross the knee and can pull the tibia toward the midline as the knee flexes. The gastrocnemius and plantaris cross the knee and, in a flexed, non‑weight‑bearing position, contribute an internal rotational component to the tibia as they help drive knee flexion. The tibialis anterior, while primarily acting on the ankle, also participates by stabilizing the leg and supporting the coordinated inward torque of the lower limb during this motion. This combination yields medial rotation of the tibia when the leg is flexed and the foot is not weight-bearing.