Humeroulnar joint
This hinge joint between the upper arm bone and the ulna allows the elbow to bend and straighten through its largest range of motion.
The elbow joint is formed by the meeting of the upper arm bone with the two forearm bones, creating a hinge that allows bending and straightening while a separate articulation between the forearm bones allows rotation.
Two bony prominences at the base of the upper arm bone, the medial and lateral epicondyles, serve as attachment points for the muscles that move the wrist and fingers, which is why so many common elbow conditions are actually tendon problems rather than joint problems.
Key structures
Proximal radioulnar joint
This joint between the two forearm bones, working together with a similar joint at the wrist, allows the forearm to rotate the hand palm-up or palm-down.
Common extensor tendon
This tendon attaches the forearm extensor muscles to the lateral epicondyle and is the primary site of irritation in tennis elbow.
Common flexor tendon
This tendon attaches the forearm flexor muscles to the medial epicondyle and is the primary site of irritation in golfer's elbow.
Ulnar collateral ligament
This ligament resists stress on the inner elbow and is particularly important in overhead throwing athletes, where repetitive stress can lead to injury.
Ulnar nerve
This nerve passes behind the inner elbow through a narrow passage and can become compressed with prolonged bending or direct pressure, producing tingling in the ring and little fingers.
Planes & range
Elbow flexion from full extension to a fully bent position represents the joint's primary hinge motion, while pronation and supination each contribute roughly 80–90° of forearm rotation.
This anatomy explains why elbow pain is so often a tendon overuse problem centered on the epicondyles rather than a joint problem, and why treatment tends to target the forearm muscles as much as the elbow itself.
Keep exploring
More in Upper limb
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The wrist and hand pack more small joints, tendons, and nerves into a small space than almost any other body region, enabling fine motor control at the cost of frequent overuse injury.
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