How do the supinator muscles turn your palm?

The supinator muscle is a broad muscle in the posterior compartment of the forearm. It is responsible for turning the palm anteriorly, which is the anatomical position. Here's how it works:

1. The supinator muscle originates from the lateral epicondyle of the humerus and the proximal part of the ulna, which are bones in your upper arm and forearm.

2. When the supinator muscle contracts, it pulls on the radius, one of the two bones in your forearm.

3. This action causes the radius to rotate around the ulna, which is the other bone in your forearm.

4. As the radius rotates, it turns the hand so that the palm faces anteriorly or upwards. This is known as supination.

5. When the muscle relaxes, the hand returns to a neutral position.

So, the supinator muscle turns your palm by rotating the radius around the ulna.