During the process of endochondral ossification the cartilaginous bone rudiment becomes vascularised, beginning in the diaphysis and continuing in the growth plate. Different stages of chondrocyte differentiation are apparent in the growth plate: resting; proliferating and hypertrophic chondrocytes; a zone of mineralisation; and a zone of blood vessel invasion and cartilage invasion, where ossification occurs. New blood vessel formation plays a major role in endochondral ossification. This process is controlled by a fine balance of stimuli and inhibitors, of which VEGF is perhaps the best characterised pro-angiogenic factor. A disruption of this angiogenic balance may promote conditions associated with pathological neovascularisation, including RA. Vascularisation of cartilage is also a feature of OA. To establish the function of VEGF-stimulated angiogenesis in endochondral bone formation.