All appendicular bones (except clavicle) develop by the endochondral (intracartilaginous) method of osteo-genesis. Mesenchymal models of limb bones are formed during the 5th week of development.However, by the end of the 6th week entire limb skeleton becomes cartilaginous.Ossification of the long bones begins in the 7th week by the appearance of primary centers of ossification in the middle of the cartilaginous models.The primary centers of ossification are present in all the long bones of each limb by the end of the 12th week of the intrauterine life.However,ossification of most of the carpal and tarsal bones begins during the first year after birth.