Foreign body induced synovitis - knee

Case contributed by Dr Maulik S Patel

Presentation

History of wood splinter injury to knee about a year ago. 1 surgery and 2 aspirations done so far. MR showing synovitis. Referred for USG to look for any residual wood splinter - foreign body.

Patient Data

Age: 14 years
Gender: Male

Knee joint

X-ray

Prominent supra and infrapatellar soft tissue.

Knee joint

Ultrasound

Synovitis in the suprapatellar region with a foreign body (5 mm) embedded within the synovium. A second foreign body (10 mm) posterior to the posterior cruciate ligament. A third foreign body (15 mm) posterior to calf vessels.

Foreign body granuloma is noted here; abutting vessels. No thrombosis was present.

Popliteal cyst as well as extra-articular collection. A reactive node in popliteal fossa adjacent to popliteal vessels.

Case Discussion

Fragmentation and migration are major causes of false-negative ultrasound when you are looking for this kind of foreign body.  

Presence of gas in soft tissue can result in false-negative or false-positive ultrasound finding.

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