Evidence-based On-call

Cellulitis

Clinical features

If a Baker's cyst is possible, look for: ^a

crepitus on flexing knee
history of arthritis
a positive ultrasound scan

Remember the presence of a Baker's cyst (ruptured or not) does not exclude a DVT. ^a

Why?

Arthritis or crepitus makes a Baker's cyst more likely

Patient	Target Disorder and Reference Standard	Diagnostic Test	LR+ (95% CI)	Post-test Probability	LR- (95% CI)	Post-test Probability
suspected DVT ^a (pre-test probability: 33%)	Baker's cyst (venography, arthroscopy)	crepitus on flexing knee	3.0 (1.2 to 7.5)	64%	0.54 (0.30 to 0.96)	24%
		history of arthritis	3.4 (1.2 to 9.4)	67%	0.59 (0.35 to 0.98)	26%
		ultrasound scan	infinity (0.16 to infinity)	100%	0.88 (0.73 to 1.1)	34%