Olecranon

Highlighted in green, the olecranon is the posterior extension of the ulna. At full extension of the elbow, the end of the olecranon fits into the olecranon fossa of the humerus.

The posterior bundle of the ulnar collateral ligament connects this part of the ulna to the humerus.

The common tendon of the triceps brachii inserts into the olecranon.