Monoarthritis

Template:DiseaseDisorder infobox Template:Search infobox Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Eiman Ghaffarpasand, M.D. [2]

Overview

Monoarthritis is inflammation (arthritis) of one joint at a time. It is usually caused by trauma, infection, or crystalline arthritis.

Causes

Septic arthritis

Septic arthritis is due to a bacterial infection to the joint. It requires urgent joint washout in the operating room followed by intravenous antibiotic therapy for large joints. Small joints or children can be treated with repeated aspirations and intravenous antibiotics.

Gout

In gout, the acute inflammatory arthritis is caused by excess uric acid caused by either overproduction or under-excretion. Before the age of menopause, women have a lower incidence than males, but the rates are equal above this age. Gout can cause mono- or polyarthritis, but usually results in monoarthritis first.

Pseudogout

When monoarthritis is caused by pseudogout (calcium pyrophosphate deposition disease, CPPD), the inflammation usually lasts days to weeks, and involves the knees in half of all attacks. Like gout, attacks can occur spontaneously or with physical trauma or metabolic stress. Patients may feel well in between pseudogout attacks, and 5% present with pseudo-rheumatoid symptoms.

Osteoarthritis

Osteoarthritis is a degenerative disease commonly involving the knees and hips. It results from erosion of the cartilage protecting the bones from rubbing together.

Diagnosis

When faced with monoarthritis, one of the main decisions to make is whether to perform a joint aspirate by inserting a needle into the affected joint and removing some fluid for microscopic analysis. This decision is largely taken on inflammatory markers in blood tests (e.g. CRP), fever and the clinical picture. The main use of aspiration is to detect bacteria and neutrophil granulocytes (in septic arthritis) and crystals (crystal arthropathies).

Differential Diagnosis of Monoarthritis

Diseases			Clinical manifestations							Para-clinical findings								Gold standard	Additional findings
			Symptoms				Physical examination
										Lab Findings				Imaging			Histopathology
			Joint Swelling	Fever	Weight loss	Claudication	Morning stiffness	Local erythema	Skin manifestation	CBC	ESR	Synovial fluid	Other	X-ray	CT scan	Other
Monoarthritis	Osteoarthritis
	Trauma
	Neoplasms
	Infection	Gonococcal infection
		Nongonococcal bacterial infections
		Mycobacterial infection
		Fungal infection
		Lyme disease	+	+	+/-	+/-	-	-	Erythema migrans	Leukopenia, Thrombocytopenia	-	Cell counts 500-98,000/µL	Microscopic hematuria, Proteinuria, ↑ALT or AST	-	-	-	Fibrosis of the deeper dermis and hyalinization of collagen bundles	Serologic tests	Erythema migrans
	Crystal-induced arthritis	Gout
		Pseudo-gout
	Systemic disorders	Reactive arthritis	+/-	+/-	-	-	-	-	Genital ulceration	Normocytic normochromic anemia	↑	High WBC count (10,000-40,000/µL)	HLA-B27 test	Periosteal reaction and proliferation of tendon insertion site	Sacroiliitis	Enthesitis in ultrasonography	Keratoderma blennorrhagicum,Balanitis circinata	Spondyloarthritis and unequivocal demonstration of preceding infection	Conjunctivitis, Uveitis
		Psoriatic arthritis	+	-	-	-	-	+	Scaly erythematous plaques, Guttate lesions, Lakes of pus, Erythroderma	Normal	↑	High WBC count (5000-15,000/µL) with >50% of PMN leukocytes	↑RF, ANA, IgA	Joint-space narrowing, Fluffy periostitis	Pencil-in-cup deformity, Early signs of synovitis	Sacroiliitic synovitis, Enthesitis in MRI	Lack of intrasynovial Igand RF, Greater propensity for fibrous ankylosis, osseous resorption, and heterotopic bone formation	Clinical findings	Onycholysis, Splinter hemorrhages
		Inflammatory bowel disease-associated arthritis	+	+	-	-	+	+/-	Pyoderma gangrenosum(ulcerative colitis),Erythema nodosum(Crohn disease)	Iron deficiency anemia, Leukocytosis, Thrombocytosis	↑	Mild to moderate inflammatory fluid, PMNpredominance	↑RF, Antiendomysial Ab,Antitransglutaminase Ab	Bilateral sacroiliitis, Syndesmophytes and apophyseal joint involvement in spine	-	Early detection of spinal and sacroiliac lesions in MRI	-	Clinical findings and history	Acute anterior uveitis
		Sarcoid periarthritis	+	-	-	-	-	-	Mild papules and nodules	Mild anemia	↑	Cell count < 25% PMNs (non-inflammatory)	IL-2 and IFN-γ, ↑ACE, ↑1, 25-dihydroxyvitamin D	Bilateral hilar adenopathy	Active alveolitis or fibrosis	Hepatosplenomegaly in ultrasonography	Noncaseating granulomas (NCGs)	Histological confirmation	Heart block, Ocular lesion
		Rheumatoid arthritis	+	-	+	+	+	-	Rheumatoid nodules	Anemia, Thrombocytosis	↑	WBC count >2000/µL (generally 5000-50,000/µL), with neutrophilpredominance (60-80%)	Anti-CCP Ab, Hyperuricemia	Joint-space narrowing	Microfractures	Synovitis in MRI	Influx of inflammatory cells into the synovial membrane, withangiogenesis	Clinical findings coupled anti-CCP antibody	Rheumatoid nodules
		Myelodysplastic and leukemic disorders

Related Chapters

• Gout
• Pseudogout
• Septic arthritis
• Osteoarthritis