There are 6 ossification centers around the elbow joint. These ossification centers all appear at different ages and they all fuse to the adjacent bones at various ages. It is not clinically important to memorize the specific ages of when these ossification centers appear or fuse. However, it is clinically important to realize that the ossification centers always appear in a specific sequence.
The mnemonic of the order of appearance of the individual ossification centers is C-R-I-T-O-E: Capitellum, Radial head, Internal (medial) epicondyle, Trochlea, Olecranon, External (lateral) epicondyle. Remember that the anatomic position of the body places the upper extremities in external rotation (supination at the elbows) such that the antecubital fossa faces anteriorly. Thus, the external epicondyle is on the radial side of the elbow, while the internal epicondyle is on the ulnar side of the elbow. The ages at which these ossification centers appear are highly variable, but as a general guide, remember 1-3-5-7-9-11 years.