Final answer:
The capitulum of the humerus articulates with the radial head, forming part of the elbow joint.
Step-by-step explanation:
The portion of the humerus that articulates with the radial head is known as the capitulum. The capitulum is a knob-like structure located on the anterior surface of the distal humerus, immediately lateral to the trochlea. It articulates with the head of the radius bone of the forearm to form part of the elbow joint.