How a Joint Moves

Muscles originate on one bone, cross over a joint, and then insert onto another bone. When the muscle pulls the joint moves. You can feel this happening by gripping onto the muscles of your upper arm.

The extensor muscles pull your hand and fingers up.

The flexor muscles pull your hand and fingers down, and are responsible for making a fist.

*Information based on research published by Travell, JG, Simons DG. Myofascial Pain and Dysfunction, The Trigger Point Manual (Book). 1983 Williams & Wilkins Publishers, Baltimore, MD.