Greater than 50 years of age
Morning stiffness for less than 30 minutes
Crepitus on active motion of the knee
Bony tenderness
Bony enlargement
No palpable warmth
Osteoarthritis
Acute osteoarthritis
Rheumatoid arthritis
Avascular necrosis
Ankylosing spondylitis
Crystal-induced 
Reactive arthritis
Gonococcal arthritis, arthritis-dermatitis syndrome