Olecranon Fossa

This is the groove on the posterior of the distal end of the humerus into which the olecranon of the ulna fits when the elbow is at or near full extension.

The majority of elbow joint stability at less than 20° of elbow flexion is skeletal.1 An important part of that skeletal support is the olecranon's fit into this fossa.

1 Cain EL Jr, Dugas JR, Wolf RS, Andrews JR. Elbow injuries in throwing athletes: a current concepts review. Am J Sports Med. 2003; 31; 621.