In an otherwise healthy 50-year-old adult, which joint is most commonly affected by native septic arthritis, and which organism is the usual cause?

• A Knee, Staphylococcus aureus ✓
• B Hip, Streptococcus pneumoniae
• C Shoulder, Escherichia coli
• D Ankle, Pseudomonas aeruginosa

Explanation

The knee accounts for roughly half of all cases of native septic arthritis in adults, followed by the hip and shoulder. Staphylococcus aureus is the most common organism across all age groups except sexually active young adults with gonococcal arthritis. Pseudomonas is associated with puncture wounds and intravenous drug use, and streptococci are second overall to staphylococci.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.