Skeletal growth about the elbow occurs at six ossification centres. The capitellum becomes visible at the age of one with further centres becoming visible every odd year from this point. The lateral epicondyle is the last centre to become visible at approximately 11 years of age.
Two counting methods are taught to help remember the ages at which the ossification centres appear: 1-3-5-7-9-11 (simple) and 1-5-7-10-10-11 (more accurate).
Fusion of the ossification centres is also age-dependant and happens one to two years earlier in girls. The capitellum, trochlea and olecranon fuse at approximately 14 years, the medial epicondyle at 15 years and the lateral epicondyle at 16 years.