The Elbow

The elbow is a synovial hinge joint made up of bone, cartilage, and ligaments that can twist and enable rotation of the hand. It is a complex joint that connects the two bones of the forearm, the ulna and radius, to the upper arm bone, the humerus. The radius is smaller than the ulna and connects to the wrist on the same side as the thumb. The lower end of the humerus bone flares out into two rounded protrusions called epicondyles, where muscles attach.

See Common Elbow Issues

The Anatomy of the Elbow

The elbow consists of two joints: the ulnohumeral joint creates the hinge between the humerus and the ulna allowing the arm to bend and straighten. The olecranon joint connects the upper part of the ulna, cupping the distal humerus.

Nerves and Vessels of the Elbow:
The elbow is crossed by important nerves and vessels for the function of the upper extremity and is the origin of the flexor–pronator and extensor–supinator musculatures of the forearm. All the nerves that travel down the arm pass across the elbow. Three main nerves begin together at the shoulder the radial nerve, the ulnar nerve, and the median nerve. These nerves are responsible for signaling your muscles to work and to relay sensations such as touch, pain, and temperature. The ulnar nerve runs just below the skin at the elbow’s “funny bone,” which is a part of the humerus. The radial nerve supplies the triceps, wrist extensors, and most of the back of the hand, while the median nerve passes down the inside of the arm and crosses the front of the elbow. At the wrist it goes through a “tunnel,” referred to as the carpal tunnel, made up of the wrist bones and a tough band of connective tissue (ligament).Joint Capsule and BursaeLike all synovial joints, the elbow joint has a capsule enclosing the joint. The joint capsule is thickened medially and laterally to form collateral ligaments, which stabilize the flexing and extending motion of the arm. The elbow bursa is a thin fluid-filled membranous sac filled with synovial fluid that is located at the bony tip of the elbow (the olecranon). It acts as a cushion to reduce friction between the moving parts of a joint, limiting degenerative damage.Ligaments of the ElbowAn extensive network of ligaments surrounding the joint capsule helps the elbow joint maintain its stability and resist mechanical stresses.

The main ligaments of the elbow are:

‍Radial collateral ligament, or lateral collateral ligament, which lies on the lateral surface of the joint and connects humerus with the ulna and with the annular ligament. This ligament is generally triangular in shape.

‍Ulnar collateral ligament, or medial collateral ligament, which lies on the medial surface of the joint and connects the inner end of the ulna with the inner end of the humerus.

‍Annular ligament, which wraps around the radial head (the word annular means “ring-shaped”). The annular ligament cinches the radius to the ulna without interfering with the rotation of the radial head.

‍Posterior ligament, which lies on the posterior surface of the joint and attaches the end of the ulna with the humerus.

‍Anterior ligament, which lies on the anterior surface of the joint.Muscles and Tendons Surrounding the ElbowThe muscles and tendons surrounding the elbow make it possible for the arm to move.

The two main muscles responsible for bending and straightening the arm at the elbow are:

‍Triceps, located at the back of the arm.

‍Biceps, located at the front of the arm.

The main muscles of the elbow involved in wrist and finger movement are:

‍Flexors, which attach to the inside of the elbow and enable you to bend your wrists and fingers.

‍Extensors, which attach to the outside of the elbow and enable you to extend or straighten your wrists and fingers.Several tendons connect the muscles and bones of the elbow.

The primary tendons are:

‍Biceps tendon, which attaches the biceps on the front of the arm to the radius, enabling you to forcefully bend your bend your elbow.

‍Triceps tendon, which attaches the triceps to the ulna, enabling you to forcefully straighten your elbow.