Differential diagnosis of calf pain with musculoskeletal ultrasound imaging.

CASE HISTORIES Case 1: Massive Baker’s cyst presenting as a deep venous thrombosis (fig 1) A 68 year old woman presented to the accident and emergency department describing a three day history of acute left calf pain and swelling associated with severe difficulty in weight bearing. She had been previously diagnosed with hypertension, peptic ulcer disease, and had had seronegative rheumatoid arthritis affecting hands, knees, and hips for the past five years. Regular drugs included celecoxib and ranitidine. She was a smoker with a body mass index of 27 and had been on an airline flight from Spain to Scotland two weeks previously. The D-dimer level was increased at 1463 mg/l and she was initially treated with Dalteparin for a presumptive diagnosis of deep venous thrombosis (DVT). A Duplex ultrasound (US) scan of the leg was performed and did not show any evidence of a DVT. The left calf pain had now increased and new bruising was noticed at the inferoposterior aspect of the left calf. Dalteparin was discontinued and musculoskeletal ultrasound (MSUS) confirmed the presence of a large Baker’s cyst extending from the popliteal fossa to the junction of the gastrocnemius and Achilles tendon, at the site of the new bruising (fig 1). The patient now admitted that calf pain and swelling had been present for several months. A diagnosis of Baker’s cyst with minor rupture was made. The left knee was aspirated and injected with little improvement in calf swelling. Two attempts to reduce the cyst by direct US guided aspiration with an 18G and 16G needle were unsuccessful. The patient declined a further surgical opinion and was managed conservatively.