Which movement is most affected after damage to the gracilis muscle?

The gracilis muscle plays a significant role in the movement and control of the hip and knee. Its primary function is to facilitate hip adduction, which involves bringing the thigh towards the midline of the body. When the gracilis is damaged, this ability to adduct the hip is compromised, leading to difficulties in movements that require bringing the legs together.

In addition to contributing to hip adduction, the gracilis assists in flexion of the knee and internal rotation when the knee is flexed. However, its primary and most direct effect is seen in the movement of hip adduction. Therefore, damage to this muscle will most notably impair the ability to adduct the hip joint, making activities that require this movement challenging.

The other movements listed, such as hip abduction, hip external rotation, and knee extension, are not primarily associated with the gracilis. Instead, different muscles are responsible for those actions, which is why they are less impacted by any injury to the gracilis.