There are two infectious diseases that will be discussed in this handout; osteomyelitis and septic arthritis. Osteomyelitis is an infection of the bone that can include the periosteum, medullary cavity, and cortical bone. Septic arthritis is an infection of the surface of the cartilage that lines the joint and the synovial fluid that lubricates the joint. In both of these diseases, Staphylococcus aureus is the most common cause of infection.

Osteomyelitis tends to take some time to cause extensive damage to the bone (e.g., several weeks). Children and elderly adults are more likely to get these infections. Children usually get osteomyelitis of the long bones and the elderly usually get osteomyelitis of the vertebral body in the lumbar region of their spine. To successfully treat osteomyelitis requires several weeks (4-6 weeks) of antibiotic therapy. In cases of extensive bone damage surgery is also required to eliminate the infection.

Two different types of arthritis are associated with microbial infections; reactive and septic or infectious arthritis. Reactive arthritis is a sterile inflammatory process in the joint that can occur following a bacterial infection at a distant site in the body. Reactive arthritis also called Reiter’s syndrome and causes urethritis, conjunctivitis, asymmetrical polyarthritis (e.g., ankles, knees, feet, and sacroiliitis), and a rash that occurs weeks after a bacterial infection. The most common cause of reactive arthritis is Chlamydia trachomatis. However, Campylobacter jejuni, Yersinia enterocolitica, Shigella, Salmonella and Streptococcus can all cause reactive arthritis. Reactive arthritis occurs more commonly in patients with human lymphocyte antigen B27 (HLA-B27).

✓ Obtain adequate tissue for culture and histopathology. A sample deep in the infected tissue is needed. Bone biopsy is usually required.

✓ Design a specific antimicrobial regimen. Usually, only one antimicrobial agent is needed if the organism is known.

✓ Surgery is not usually needed in acute hematogenous osteomyelitis surgery however, 4-6 weeks of antibiotic treatment is required. Patients with chronic osteomyelitis usually require surgery.