Plant Thorn Synovitis (cont.)

Plant thorn arthritis is suspected in a patient who presents with a single joint that is inflamed after it has been punctured by a plant thorn. This is true even if the patient recalls removing the thorn, as described above, because the thorn can leave behind tiny fragments of thorn matter that leads to the chronic inflammation of plant thorn arthritis.

Removal of joint fluid (joint aspiration) is performed to rule out bacterial or fungal infection of the joint.

Ultimately, the diagnosis of plant thorn arthritis requires either detection of a piece of thorn within the joint by radiology testing or surgical removal of the thorn fragments and identification of the fragments microscopically in the laboratory. Sometimes tiny pieces of thorns can be visualized using magnetic resonance imaging (MRI scanning), high-resolution computerized tomography (HR-CAT scanning), or ultrasound imaging. Often, however, the residual thorn fragments are too small to be seen with these methods and are detected only when identified in tissue that is surgically removed from the joint.

The affected joint lining tissue (synovium) is examined in the pathology department using microscopes. The tissue forms a characteristic reaction, called a granulomatous reaction, within the synovium (granulomatous synovitis). The microscopic thorn fragments are easily identified using a polarized light microscope as they appear brilliantly shiny (birefringent) to the examining pathologist.

Source: MedicineNet.com
http://www.medicinenet.com/plant_thorn_synovitis/article.htm