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
Prominent supra and infrapatellar soft tissue.
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.