Olecranon fossa
The olecranon fossa is a deep triangular depression on the posterior side of the humerus, superior to the trochlea. It provides space for the olecranon of the ulna during extension of the forearm.
Structure
The olecranon fossa is located on the posterior side of the distal humerus.The joint capsule of the elbow attaches to the humerus just proximal to the olecranon fossa.