Presentation
A boy had a right knee anteromedial aspect penetrating trauma due to a thorn about 2 weeks prior. He presented with complaints of knee pain, swelling, and restricted movements.
Patient Data
There is an oblique short hypoechoic track in the anterior medial soft tissue of knee at the site of the entry wound. There is a moderate suprapatellar effusion along with synovial hypertrophy in the suprapatellar region. There is a linear focus ( about 15 mm long ) abutting the posterior aspect of lateral femoral condyle; aligned to the femoral long axis.
1st image: an intraoperative photo showing a foreign body deep in the tissue.
2nd image: extracted thorn.
Case Discussion
A boy had a knee penetrating injury due to a thorn. He developed pain, diffuse swelling involving the knee and restricted movement. Ultrasound shows a small entry track in the anterior medial aspect of the knee with severe synovitis. There is a linear focus (foreign body) abutting the posterior aspect of lateral femoral condyle; which was removed by surgery.
A foreign body in a joint cavity can cause synovitis.
Two points should be remembered while scanning for a suspected foreign body in a joint or soft tissues, migration and fragmentation of a foreign body. It is not necessary that a foreign body is in the vicinity of the entry point as in this case. A foreign body may get fragmented in the joint or soft tissues resulting in more than one foreign body. One should not stop searching for another foreign body after detecting first.
Intraoperative photos courtesy operating surgeon Dr. Pinkesh V. Patel.
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