It is directly adjacent to the radial fossa of the humerus.

The ulna has a deep radial fossa.

In full flexion the head similarly reaches beyond the capitulum to enter the shallow radial fossa on the anterior side of the humerus.

The radius is shifted cranially, and a radial fossa allows for the ulna to cradle the radius craniolaterally.

The lower extremity consists of 2 epicondyles, 2 processes (trochlea & capitulum), and 3 fossae (radial fossa, coronoid fossa, and olecranon fossa).

Above the front part of the capitulum is a slight depression, the radial fossa, which receives the anterior border of the head of the radius, when the forearm is flexed.