Final answer:
A muscle that abducts the thigh crosses the hip on the lateral side of the joint. The antagonist muscle would adduct the thigh, moving it towards the midline.
Step-by-step explanation:
A muscle that abducts the thigh would cross the hip on the lateral side of the joint.
The antagonist muscle, which performs the opposite action, would be a muscle that adducts the thigh, moving it towards the midline.