Acute monoarthritis is a common complaint in the emergency department. The differential for acute monoarthritis is broad. A delay in proper diagnosis and treatment of certain etiologies can result in significant morbidity.1,2 The evaluation of a patient with acute monoarthritis should begin with a focused history and physical exam which will guide further laboratory and radiographic studies. With a history of trauma or focal bony pain, radiography can be useful to rule out a fracture or tumour. In an acutely inflamed joint with an effusion and no history of trauma, arthrocentesis is necessary to differentiate between septic arthritis, crystal arthritis or an inflammatory effusion from intra-articular derangement.1
The OSTRICH mnemonic can be helpful in remembering the differential for monoarthritis:
Tumor– chondrosarcoma, osteoid osteoma, tenosynovial giant cell tumor, metastatic disease2
Rheumatic and auto-immune disease – rheumatoid arthritis, spondyloarthritis, systemic lupus erythematosus, sarcoidosis2
Intra-articular pathology – meniscal tear, osteonecrosis, fracture
Crystal arthropathy – monosodium urate, calcium pyrophosphate dihydrate
Hemarthrosis – trauma, clotting disorders, anticoagulation
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- 1.Becker J, Daily J, Pohlgeers K. Acute Monoarthritis: Diagnosis in Adults. Am Fam Physician. 2016;94(10):810-816. https://www.ncbi.nlm.nih.gov/pubmed/27929277.
- 2.Ramirez Curtis M. Overview of Monoarthritis in Adults. UpToDate. https://www.uptodate.com/contents/overview-of- monoarthritis-in-adults . Published 2017. Accessed May 20, 2019.