Staphylococcus aureus is the most common (about 90%) organism isolated in septic ahritis in adults. In neonates joint sepsis is caused by S. aureus with group B streptococci being the next most common. In young children aged 2 months to 2 years, S. aureus, Streptococcus and Haemophilus influenza in an decreasing order. In young adults, S. aureus and N. gonorrhoeae are the most common organisms causing joint sepsis. In elderly people, S.aureus causes infection. Gram negative septic ahritis may occur in patients with sickle cell anemia.