Three bones come together to form the elbow joint: the lower end of the humerus (upper arm bone), the upper end of the radius (forearm bone on the thumb side) and the upper end of the ulna (forearm bone on the pinky side).
The elbow is a hinge joint; it enables us to bend and straighten our arm.
Elbow bone and joint
Muscles, ligaments and tendons hold the elbow joint together and stabilize it.
There are three ligaments in the elbow: the ulnar collateral ligament, radial collateral ligament and annular ligament.
Several muscle groups cross over the elbow joint. The muscles involved in flexion (bending) the elbow are the biceps brachii, brachioradialis and the brachialis. The triceps are responsible for elbow extension (straightening the arm).
The muscles involved in wrist extension originate in the lateral side of the elbow (when your palm is facing up, it's the outside part of elbow). The muscles involved in wrist flexion are found in the medial side of the elbow (palm facing up, inside part of elbow.) These muscle groups are also responsible for the forearm movement that enables us to turn our palm up and down.
Normal Range of Motion
Normal elbow range of motion consists of being able to extend the arm out completely and bend it back so your finger tips can touch the top of your shoulder.