The elbow is a hinge that bends and straightens the arm, combined with a pivot that turns the forearm. Three bones meet inside one joint capsule.
Three joints in one
The humerus and ulna form the main hinge for flexion and extension. The humerus also meets the radial head, and the proximal radioulnar joint lets the radius spin for pronation and supination.
Ligaments
The ulnar (medial) collateral ligament resists valgus stress and is often injured in throwing athletes. The radial collateral ligament supports the outer side, and the annular ligament wraps around the radial head.
Nerves and vessels
The ulnar nerve runs behind the medial epicondyle, the spot known as the funny bone. The median nerve and brachial artery cross the front of the elbow, and the radial nerve passes on the lateral side.
Common problems
Lateral epicondylitis (tennis elbow) and medial epicondylitis (golfer's elbow) are overuse injuries of tendon attachments. In young children, a sudden pull on the arm can slip the radial head out of the annular ligament (nursemaid's elbow).
| Structure | Where it runs | How to check |
|---|---|---|
| Ulnar nerve | Behind the medial epicondyle | Little finger sensation, spreading the fingers |
| Median nerve | Front of the elbow | Thumb and index pinch (OK sign) |
| Radial nerve | Lateral side | Wrist and finger extension |
| Brachial artery | Front of the elbow | Radial pulse, capillary refill |
At the bedside
Elbow fractures in children, especially supracondylar fractures, can injure the brachial artery and nearby nerves. Check the radial pulse, capillary refill and all three nerves of the hand before and after splinting.
Related guides
Written by Making Synapses. Topic reference: OpenStax, Anatomy and Physiology 2e (no text adapted).