Bone and joint infection basics

by Michael Held & Maritz Laubscher

Learning objectives

  1. Know the pathophysiology and differences between children and adults.
  2. Know the risk factors.
  3. Understand the most common pathogens and know how to approach


Bone and joint infections can be acute or chronic. Acute infections should be treated as orthopaedic emergency. Especially for children and immunocompromised patients infections, acute infections can lead to severe systemic illness and can have detrimental long term morbidity if not treated urgently. Osteomyeltits (infection of bone) can be divided into acute, sub-acute and chronic. In sub-acute osteomyelitis, infection lasts from one to several months, after which chronicity begins. Chronic osteomyelitis is characterised by progressive bone destruction and new bone apposition.



Compared to children, adult osteomyelitis is rarely hematogenous, i.e. originated or transported by blood. When it occurs, it usually affects the spine. It is caused by microorganisms that seed the bone in the event of bacteremia. The most common organism found in hematogenous spread is Staphylococcus aureus. Hematogenous infections are most common in children. The metaphysis is the most common site because it is rich in blood supply (although this has sluggish flow) and is an actively growing part of bone. It also has relatively fewer phagocytes than the physis or diaphysis.

Contiguous spread

This mode of contamination can be associated with previous surgery, an old non healing wound (diabetic foot, neuropathic ulcer) or a previous trauma. Infection spread by contiguity from adjacent tissue to bone.

Direct inoculation

Open fractures, penetrating injuries or bone surgeries can be a direct source of infection, resulting in osteomyelitis.

Risk factors


Osteomyelitis may be classified based on the duration of illness (acute versus chronic) and the mechanism of infection (haematogenous versus non- haematogenous).

Bacteriology and antibiotics

The most common infecting organism is staphylococcus aureus in all age groups, which accounts for 80–90% of positive cultures. The table below shows common organisms of different age groups and patient populations with antibiotic choice, but this should be guided by local authorities.

Patient cohort and bacteriology Antibiotics
Neonates S. aureus (MRSA), Group Cloxacillin (Fusidic Acid)
B strep 3rd gen cephalosporin
Gram negatives
6 months – 4 years S. aureus, K. kingae, H. Cloxacillin
influenzae (rare) + Ampicillin/3rd gen cephalosporin
> 4 years S. aureus Cloxacillin
Adults (acute) S. aureus
Penicillin allergy Clindamycin
immunocompromised S. aureus, S. pneumoniae, Cloxacillin + 3rd gen cephalosporin
pseudomonas, fungal Cloaxillin + 3rd gen cephalosporin
Cefazolin is an alternative to Cloxacillin
Sickle cell disease S. aureus, Salmonella (if not available)
contiguous chronic The most common causative Common organisms of different age
osteomyeliti organisms are: groups and patient populations with
Enterobacteriaceae sp. antibiotic choice
Staphylococcus sp.
Pseudomonas aeruginosa
Enterococcus sp.
In 45% of infections multiple
organisms cultured
heamatogenous chronic Staphylocossus aureua is
osteomyelitis the most common organism involved in adults (60-90%)