Don't forget the ruptured Baker's cyst
Editor - The cover of the issue of 9 October shows a leg with
bruising behind the knee, extending to the mid calf and down the ankle.
The image is used to illustrate a below knee deep vein thrombosis. The
accompanying paper concludes that deep vein thrombosis can be effectively
excluded in suspected patients if the clinical probability is judged to be
low or moderate, and a D-Dimer test is negative. Ultrasound testing in
such cases is unnecessary1.
The amount of bruising shown in the picture is far in excess of that
seen commonly in deep vein thrombosis. The classical picture of a ruptured
Baker’s cyst is that of swelling behind the knee tracking down the calf,
sometimes with bruising at the ankle. However presentation similar to that
shown is not uncommon. It is therefore important to highlight this in the
differential diagnosis. Clinical examination is not always helpful. If
this paper’s suggestions are followed, a negative D-Dimer would preclude
ultrasound scanning in many cases.
Ruptured Baker’s cysts are a significant cause of pain and
disability, which can be helped by prompt treatment. It is recognised that
Baker’s cysts do not necessarily need a background of pre-existing disease
to occur and may occur in normal knee joints2. They can, and do co-exist
with a deep vein thrombosis
There is significant morbidity associated with Baker’s cyst rupture
and so it is important to consider this as a potential diagnosis in
patients with calf or knee pain, even though a D-Dimer may well be
negative. Ultrasound scanning is extremely useful in diagnosis.
Chris Holroyd, Specialist Registrar,
Richard Hull, Consultant.
Department of Rheumatology,
Queen Alexandra hospital, Portsmouth PO6 3LY
1. Fancher TL, White RH, Kravitz RL; Combined use of rapid D-dimer
testing and estimation of clinical probability in the diagnosis of deep
vein thrombosis: systemic review. BMJ 2004; 329:821-824
2. Macfarlane DG, Bacon PA; Popliteal cyst rupture in normal knee
joints. BMJ 1980; 281:1203-1204
Competing interests: No competing interests