The humerus bone is in the arm. The elbow is the joint that connects a person’s upper arm Humerus with the forearm. The humerus ( the long bone in the upper arm) and the radius and ulna (the bones of the forearm) meet at the elbow. The three bone connections form three smaller joints within the elbow joint. These smaller joints permit certain movements. The humerus ulna joint and the humerus radius joint allow a person to bend the forearm up and down. The radius ulna joint and the humerus radius joint permit a person to rotate the forearm and to turn the palm up and down. A capsule (pouch) of tough connective tissue surrounds the elbow joint. This capsule and several ligaments hold the bones in place.
Excessive or violent twisting of the forearm may injure the elbow ligaments, capsule, or tendons. One such injury, sometimes called tennis elbow, often results from playing tennis.