Osteomyelitis is a bacterial, or fungal, infection of the bone. Osteomyelitis affects about 2 out of every 10,000 people. It can result from an infection somewhere else in the body that has spread to the bone, or it can start in the bone — often as a result of an injury. Infections can reach a bone by traveling through the bloodstream or spreading from nearby tissue. Infections can also begin in the bone itself if an injury exposes the bone to germs.