How are the radius and ulna connected to the humerus at the elbow?

The elbow is a hinge joint formed by the articulation of the humerus with the radius and ulna bones of the forearm. The lower end of the humerus features two distinct articular surfaces that facilitate these connections:123

• Humeroulnar Joint: The spool-shaped trochlea of the humerus fits into the large, C-shaped trochlear notch of the ulna. This connection is primarily responsible for the bending and extension of the elbow. As the elbow moves, the ulna’s olecranon process and coronoid process fit into the olecranon and coronoid fossae of the humerus, respectively.142
• Humeroradial Joint: The dome-shaped lateral condyle (capitulum) of the humerus articulates with a shallow depression on the head of the radius.12

In addition to these connections with the humerus, the edge of the radial head also fits into a shallow groove on the side of the ulna, which allows for the rotational movements of the forearm.14