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Medical Author:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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Medical Editor:

Catherine Burt Driver, MD

Catherine Burt Driver, MD

Catherine Burt Driver, MD, is board certified in internal medicine and rheumatology by the American Board of Internal Medicine. Dr. Driver is a member of the American College of Rheumatology. She currently is in active practice in the field of rheumatology in Mission Viejo, Calif., where she is a partner in Mission Internal Medical Group.

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In this Article

• What is plant thorn arthritis?
• What plants cause plant thorn arthritis?
• What joints are typically involved in plant thorn arthritis?
• What are plant thorn arthritis symptoms and signs?
• How is plant thorn arthritis diagnosed?
• What is the treatment for plant thorn arthritis?
• What is the outlook (prognosis) of plant thorn arthritis?
• Plant Thorn Arthritis At A Glance
• Find a local Doctor in your town
• Plant Thorn Synovitis Index

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.

Pathology photo showing multinucleated giant cell granulomatous reaction (triangle point), synovial hyperplasia, fibrosis, and adjacent foreign vegetable matter (arrow with thorn fragments) with hematoxylin and eosin stain (H&E stain). Kindly provided by Xiaohui (Sheila) Zhao, MD, PhD, of the Department of Pathology and Laboratory Medicine, University of California, Irvine Medical Center.

Pathology photo showing thorn material (blue and yellow birefringent material) visualized under polarized light microscopy. Kindly provided by Xiaohui (Sheila) Zhao, MD, PhD, of Department of Pathology and Laboratory Medicine, University of California, Irvine Medical Center.