The optimality of bone's internal architecture and its remodelling is investigated by applying topological optimisation. The os-calcis (heel bone) which is subject to a relatively simple loading environment was used as the test problem. The solution is compared with X-ray and CT images of the os-calcis and is demonstrated to agree favourably with the bone's typical trabecular orientation in the coronal plane. The optimality of bone remodelling is further investigated by applying a perturbation during optimisation which leads to a different optimum topology. This is compared with in-vivo experimental results from a model in which the same perturbation was applied. The findings indicate that there may exist more than one optimum state for the same mechanical condition and that structural optimisation. is able to find these multiple states. It is therefore suggested that structural optimisation can be used to investigate the mechanisms of bone remodelling. (c) 2007 Elsevier Ltd. All rights reserved.