From the Podiatry Management news article:
Osteomyelitis is described as a broad group of infectious diseases that involves the bone and/or bone marrow.
It can arise hematogenously via extension from a contiguous infection, or by direct inoculation during surgery or trauma.
Patients with soft tissue infections or skin ulcerations that have been present for more than a week, especially if located over a bony prominence, are at risk for contiguous bone involvement.
Read more at the link: http://www.podiatrym.com/pdf/2018/11/YangWu1118web.pdf