Thorn-induced Injury of the Knee Mimicking Pigmented Villonodular Synovitis (PVNS): A Case Report

Background and Aims: Plain film radiography is the first imaging modality in the detection of most foreign bodies. However, it is not sensitive for detection of radiolucent objects such as organic material including plant thorns. Case report: Herein, we present the case of a 19-year-old male patient, presenting with an 8-month history of right knee pain and laxity, whose radiographic appearance mimicked that of pigmented villonodular synovitis (PVNS) but was found to have a retained neglected plant thorn in his knee. Upon ultrasound evaluation for image-guided biopsy to confirm the provisional diagnosis of PVNS, he was found to have a retained neglected plant thorn in his knee. Discussion: Plant thorn injuries can present as knee synovitis, as in our case, and should be kept in the differential diagnosis. An ultrasound-guided removal is possible and is a useful minimally invasive procedure.