Enhanced bone attachment to orthopaedic implants is obtained with the use of bioactive hydroxyapatite (HA) coatings. Osteoblast cells attached to both low and high crystalline HA coatings, and did not significantly change the morphology of the surfaces. Significant changes in coating chemistry took place in both low and high crystalline coatings as evidenced by the changes in the X-ray spectra of the two materials. This in vitro study had different influences on the two coating types: the low crystalline HA coating lost amorphous material and increased in crystallinity over the 14 days, while the high crystalline HA coating had a decreasing crystallinity over the same time period. The crystallographic changes taking place in the HA coatings between 7 and 14 days need to be further investigated