Most important diagnostic consideration in acute joint pain (can destroy joint in days)
Knee most commonly involved in adults; hip most common in pediatric
Most often seen in patients >65yr
Most common causative organisms
<35 y/o N. gonorrhoeae
>35 y/o S. aureus
<35 y/o N. gonorrhoeae
>35 y/o S. aureus
Septic arthritis
Transient 
Monoarticular arthritis
Abscess
Reactive arthritis
Cellulitis
Septic bursitis
Primary rheumatologic disorder 