Question

why are at least two muscles needed to move any joint in the body​

Answer 1

Explanation:

Generally, two skeletal muscles are joined to one bone, so that when one muscle contracts in one direction for enabling the bone to move in that specific direction; the other muscle becomes relaxed to facilitate the movement of the bone.

Answer 2

Answer:

Generally, two skeletal muscles are joined to one bone, so that when one muscle contracts in one direction for enabling the bone to move in that specific direction; the other muscle becomes relaxed to facilitate the movement of the bone