Injuries and Conditions: The Upper Arm

The upper arm consists of the long arm bone known as the humerus. It is attached to the shoulder blade, or scapula. The "ball-shapped" end of the humerus rests within a shallow cup called the glenoid fossa, which is located in the scapula. The opposite end of the humerus meets the radius, as well as the ulna at the elbow - forming a hinge joint allowing the arm to straighten and bend.

Triceps Muscle
Halfway down the humerus bone, the deltoid muscle attaches. The large triceps muscle, triceps brachii, is located at the back of the upper arm and attaches to the portion of the ulna called the olecranon. This becomes part of a single muscle group with three different segments, or heads - the long head, which originates on the border of the shoulder blade and is responsible for pulling the upper arm from above the head down to the floor; the lateral head, which originates on the outside of the humerus; and the medial head, which originates at the back of the humerus.

The main function of each head is to extend the forearm and straighten the elbow. Each head originates in a different place but comes together at a single tendon that attaches to the back of the ulna at the olecranon process. This muscle is attached to the bone by the triceps tendon, which inserts into the back of the elbow, and permits the straightening of the elbow when it contracts.

The radial nerve travels down the arm and supplies movement to the triceps muscle.

Biceps MuscleThe biceps muscle, or biceps brachii, is located at the front of the humerus - permitting the bending of the elbow when it contracts, as well as rotation of the forearm.

The ends of the biceps muscle are firmly attached to the periosteum by strong tendons. The upper end of the muscle is attached to the scapula by two tendons and the lower is attached to the radius of the forearm. The radius is moved upwards as the biceps contracts. The biceps muscle is connected to the bone by the biceps tendon - the proximal biceps tendon is located at the shoulder joint and the distal biceps tendon at the elbow joint.

Medical conditions most often associated with the upper arm include radial nerve dysfunction as well as inflammation and rupture of the triceps and biceps tendons - particularly among athletes.