Acute osteomyelitis: The metaphysis is commonly involved. The end vessels of the nutrient aery empty into much larger sinusoidal veins, causing a slow and turbulent flow of blood at this junction. Low oxygen tension in this region may compromise phagocytic activity of white blood cells. These conditions predispose bacteria to migrate through adjacent gaps in the endothelium and adhere to the matrix. Also, Must know: Staphylococcus aureus, Streptococcus, and Haemophilus influenzae are the most common causes of acute hematogenous osteomyelitis in children. The most common causes of septic ahritis are Neisseria gonorrhoeae, S. aureus, and group A Streptococcus. Bacterial Species Associated with Common Conditions: Staphylococcus aureus Most common organism in osteomyelitis, acute hematogenous osteomyelitis (90%), and infected metal implants. Group B strep Infants < 1 year old Haemophilus influenzae Children 1-16 years old Pseudomonas aeruginosa Nosocomial, puncture wound through shoe Pasteurella multocida Animal bite Eikenella corrodens Human bite Salmonella Sickle cell disease Anaerobes Diabetic ulcers, fight bites Candida albicans Immunocompromised Aspergillus Immunocompromised Atypical mycobacteria Immunocompromised Escherichia coli Neonatal Neisseria gonorrhoeae Septic ahritis in young sexually active adult Ref: Wilson S.C., Skinner H.B. (2006). Chapter 8. Ohopedic Infections. In H.B. Skinner (Ed), CURRENT Diagnosis & Treatment in Ohopedics, 4e.