Osteomyelitis can happen in any bone, but in rabbits (and some other animals) it is most often seen in the jaw, and is often secondary to tooth problems. Bacteria from infected or abscessed teeth can spread to the bone and cause infection in the bone. Abscesses and infections like this are hard to treat in rabbits partly because the rabbit's immune system walls off infections and the pus produced is often quite thick and doesn't drain well, making it hard to get antibiotics to the site of the infection. In addition, some antibiotics are lethal to rabbits (upset the natural funtion of the gastrointestinal tract), so antibiotics must be chosen very carefully and safe choices are limited.
Osteomyelitis is usually detected when a rabbit's owner notices hard swelling on a bone (e.g. along the jaw, or on other bones), which often increases in size surprisingly fast. If dental disease is present, the rabbit may exhibit excessive salivation (drooling), tooth grinding, decreased appetite, bad breath, soft stools, and if the problems are long-standing rabbits may become quite emaciated, dehydrated, and develop secondary problems such as fatty liver.
There are a variety of treatment options used to treat osteomyelitis, including aggressive surgery to remove infected tissue, removal of involved teeth, placement of antibiotic containing implants to treat infection, and injected or oral antibiotics.
Even with aggressive treatment, the prognosis for rabbits with osteomyelitis is poor, however. The infection sometimes responds poorly to treatment or comes back, and some rabbits develop secondary health problems. Early treatment is vital; if your rabbit has dental problems or develops lumps on the jaw, a good rabbit vet should be consulted as soon as possible to discuss treatment options.
For a glimpse into the struggle to treat osteomyelitis in rabbits, see "Fred's Story" by guest author Victoria Carey.