DOI: 10.1097/01.inf.0000083850.54807.e9

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Issn Print: 0891-3668

Publication Date: 2003/09/01


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Bilateral Baker’s cysts

Tim Nicholls

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Excerpt

A previously healthy 13-year-old boy presented to the emergency department with a 3-day history of worsening left knee pain. He described an area of swelling in the left popliteal region that later progressed to left calf pain, swelling and warmth. The pain prevented walking or bearing weight. He had no history of trauma, fever, rash, sore throat, rheumatologic disease or bleeding disorder. He reported a month-long episode of poor energy, anorexia and weight loss 1 year before this presentation that resolved without treatment. The ailment was attributed to the anxiety of starting middle school. He fell and broke his left humerus 1 year before presentation. His mother recently developed arthritis in both hands. He lives in Piedmont, a district near Oakland, CA. In the year before his symptoms, he traveled to Spain and northern Italy. He camped often in the summer months of every year. In the 2 months before his symptoms, he camped in California’s Napa County, Mendocino County and Kern County.
He was not ill-appearing, with a temperature of 37.6°C, heart rate 115 beats/min, respiratory rate 24 breaths/min and blood pressure of 107/73 mm Hg. His weight was 46.2 kg. The left knee was tender, warm and swollen. Pain prevented full knee extension, knee flexion >90 degrees and plantar flexion of the left ankle. The remainder of the physical examination was normal.
Laboratory studies revealed a white blood cell count of 7500/mm3 with 70% neutrophils, 11% band forms, 10% lymphocytes, 5% reactive lymphocytes and 4% monocytes. Erythrocyte sedimentation rate was 31 mm/h, and C-reactive protein was 4.9 mg/dl. Creatine kinase, transaminases, prothrombin time and partial thromboplastin time were normal. Radiographs of the left knee revealed a benign posterior exostosis of the proximal tibia and joint effusion.
He was sent home from the emergency department with presumed diagnosis of hemarthrosis, possibly secondary to mechanical injury. That night he had a fever of 102°F. He returned to the emergency department the next day because of worsening of the calf pain and swelling. On physical examination he was afebrile. He held his knee fixed in a position of 45 degrees of flexion. His left knee was tense with effusion. The joint was not red or warm but was tender with movement. He had a nontender area of left popliteal fullness. He had a mildly tender area of diffuse swelling around the left calf without swelling of the foot or ankle. He had tenderness with plantar flexion of his left ankle.
Gram-stained smear from the fluid of his left knee revealed no organisms, and bacterial culture showed no growth. Examination of the fluid revealed 58 500 white blood cells/mm3, of which 99% were neutrophils, and 5000 red blood cells/mm3. Ultrasound examination of the left lower extremity revealed left knee joint effusion and a large fluid collection with internal debris in the calf between the subcutaneous layer and the gastrocnemius. No definitive communication between this collection and the knee joint was detected. The differential diagnosis included Baker’s cyst (hemorrhagic), abscess, infected hemangioma or lymphangioma. Doppler flow examination revealed no obstruction to venous flow.
Treatment with cefazolin was started on admission. The next day the patient developed pain that limited rotation of the left hip, right knee pain and the presence of a firm right popliteal cyst. Examination of his left hip revealed pain that limited rotation. Examination of his right knee revealed an effusion, inability to fully extend the knee and a 2-cm firm, nontender, immobile popliteal nodule without overlying skin changes or matting. Antibacterial therapy was broadened and changed to oxacillin and ceftriaxone.
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