Step	Question			Action
1	Has there been a recent injury and at least one of the following predictors of fracture?			Plain films
		Age > 55 years
		Tenderness at head of fibula or isolated to the patella
		Inability to bear weight for at least four steps of walking
		Inability to flex knee >90 degrees
2	Is there effusion?			Arthrocentesis (especially to rule out infectious or crystalline arthritis)
3	Does the physical examination suggest meniscal or ligamentous injury, or a history of locking or giving-way sensation?			Orthopedic referral (for examination and decision on need for magnetic resonance imaging or arthroscopy)
4	Are there clinical criteria suggesting osteoarthritis? At least three of the following:			Symptomatic treatment, including:
		History		Analgesics (such as acetaminophen or nonsteroidal anti-inflammatory drugs)
			Age >50 years		Exercise
			Morning stiffness lasting >30 minutes	Plain films may be considered, although evidence for their utility is weak.
			Physical examination
			Crepitus
			Bony enlargement
			No palpable warmth
5	Is there evidence of a systemic rheumatologic disorder (such as rheumatoid arthritis, seronegative inflammatory arthropathy, or reactive arthropathy)?			Serum rheumatologic assays
					Rheumatoid arthritis: rheumatoid factor
					Systemic lupus erythematosus: antinuclear antibody
			Polyarticular involvement, especially the hands
			Morning stiffness lasting > 30 minutes
6	Does the pain persist or remain undiagnosed despite symptomatic treatment and clinical follow-up?			Rheumatology or orthopedic referral