The commonest cailage to ossify is

The epiphyseal plate (or epiphysial plate, physis, or growth plate) is a hyaline cailage plate in the metaphysis at each end of a long bone. It is the pa of a long bone where new bone growth takes place; that is, the whole bone is alive, with maintenance remodeling throughout its existing bone tissue, but the growth plate is the place where the long bone grows longer (adds length). The plate is not only found in children and adolescents; in adults, who have stopped growing, the plate is replaced by an epiphyseal line. This replacement is known as epiphyseal closure or growth plate fusion. Complete fusion happens between ages 12-16 for girls and 14-19 for boys. Ref - Medscape.com