The elbow joint is made up of bone, cartilage, and ligaments. Muscles and tendons help the elbow joint move. Dr. Patel, can you tell us more about the anatomy of the elbow?
Sure, Major Spencer. The elbow is where the bone of the upper arm, called the humerus, meets the two bones of the forearm, called the radius and the ulna. There are actually two joints in the elbow. The ulnohumeral joint is the hinge between the humerus and the ulna that enables the arm to bend and straighten. The olecranon is the upper part of the ulna that cups the lower end of the humerus, called the distal humerus.
The radiocapitellar joint is where the humerus and the radius meet, allowing for rotation of the forearm so that the hand can be turned palm up or palm down. The radial head is the knobby end of the radius that rotates around the ulna. Fluid-filled sacs called bursal sacs provide cushioning and reduce friction in these joints.
Ligaments, which are tough, fibrous tissues that connect bone to bone, surround the elbow joint. The thicker ligaments on the inner and outer sides of the elbow, called collateral ligaments, hold the elbow joint together and prevent dislocation. On the inside of the elbow is the ulnar collateral ligament, or UCL. The radial collateral ligament and the lateral collateral ligament are on the outside of the elbow.
Several muscles and tendons cross at the elbow. The flexor/pronator muscles of the forearm and wrist begin at the elbow. The forearm tendons, often called extensors, attach the forearm muscles to bone. One of these tendons is called the extensor carpi radialis brevis, or ECRB. The ECRB attaches forearm muscles to the lateral epicondyle, a bony bump on the bottom of the humerus.
Three major nerves cross at the elbow, including the ulnar nerve, which controls the muscles of the hand and provides sensation to the small and ring fingers. The ulnar nerve runs through the cubital tunnel, which is a passageway formed by a bony bump called the medial epicondyle and the olecranon. Where the ulnar nerve runs under the medial epicondyle is sometimes called “the funny bone” because bumping it causes a shock-like, tingling sensation.