The differential diagnosis of bone lesions in treponemal disease is well established in palaeopathology. However, the actual mechanism responsible for the characteristic distribution of bone involvement is not as clear. Two mechanisms are proposed in the literature. Firstly, that bone lesions are the result of direct extension from the skin rash of the secondary stage of disease. Secondly, that bones situated closer to the skin are more vulnerable to local trauma and therefore more likely to elicit a subperiosteal bone response. We propose an alternative explanation for the characteristic distribution of bone lesions in treponemal disease. This explanation is based on the close association between the lymphatic and skeletal systems and the pathogenesis of treponemal disease. This paper argues that the position of the lymphatic nodes and vessels, with little soft tissue intervention between bone tissue, mirrors the characteristic pattern of skeletal involvement in treponemal disease. Copyright © 2002 John Wiley & Sons, Ltd.