Monoarthritis

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

Differential Diagnosis of Monoarthritis

Differentiating the diseases that can cause monoathritis:

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		+	-	-	-	-	-	Heberden nodes	Anemia	-	Noninflammatory joint fluid	Urinary pyridinium cross-links	Joint-space loss, Subchondral bony sclerosis, Cyst formation	Malalignment of the patellofemoral joint	Early diagnosis of osteoarthritis of the hand with bone scan	-	Clinical findings	Microfracture, Bone pain
	Trauma		+	-	-	-	-	+	Wound or laceration	-	-	Hemarthrosis	-	Severe joint effusion, Fracture	Fracture, Synovial tear	-	-	X-ray	Deformity, Severe pain
	Neoplasms		+	-	+	+/-	-	-	Rash	Normocytic normochromic anemia	↑	High WBC count (10,000-40,000/µL)	Hypercalcemia, Hyperphosphatemia	Peri-articular osteoblastic or osteoclastic lesion	Elevation of the periosteum	Intense radionuclide uptake in bone scan	Spindle-shaped and atypical stromal cells, with irregular nuclei	Clinical findings and imaging	Nocturnal pain, Pathologic fractures
	Infection	Gonococcal infection	+	+	-	-	-	+	Maculopapular, Pustular, Vesicular lesions on an erythematous base	Leukocytosis	↑	Purulent with cell count > 50,000 WBC/µL (with PMNs > 90%)	Blood and synovial fluid culture	Minor articular damage	-	-	Dermal vasculitis with perivascular neutrophils	Nucleic acid amplification tests (NAATs)	Dermatitis, Tenosynovitis
		Nongonococcal bacterial infections	+	+	-	-	-	+	Local erythema	Leukocytosis	↑	Purulent with cell count > 50,000 WBC/µL (with PMNs > 90%)	Blood and synovial fluid culture	Joint effusion, Cartilage destruction, Joint space narrowing	Sternoclavicular or sacroiliac joint infections	Periarticular osteomyelitis in MRI	-	Synovial fluid culture	Limping, Malaise
		Mycobacterial infection	-	+	+	+	+/-	-	Local erythema	Leukocytosis, Normocytic normochromic anemia	↑	Moderately elevated WBC counts (neutrophilic predominance), low glucose, and increased protein	PPD	Tissue swelling, Bone destruction with normal joint space, Osteopenia	Vertebral anterior portion collapse	Complicated effusion with partial joint destruction and erosion in MRI	Granulomatous inflammation	Synovial fluid culture	Limping, Malaise, Chronic cough
		Fungal infection	-	+/-	-	-	-	+/-	Local eczema, Local erythema	Eosinophilia, Leukocytosis	↑	WBC counts range from 9,000-43,000/µL (PMNs predominance)	Direct microscopy	Joint effusion, Dislocation of the joint, Metaphyseal irregularities and punched out lesions	Articular erosion	-	Villonodular synovitis, Typical pannus, Non-caseating granulomas, Spherules containing coccidioidal endospores	Synovial histopathology	Malaise, Tenderness
		Lyme disease	+	+	+/-	+/-	-	-	Erythema migrans	Leukopenia, Thrombocytopenia	-	Cell counts 500-98,000/µL	Microscopic hematuria, Proteinuria, ↑ALT or AST	Knee joint effusion. Intra-articular edema	-	Unspecific effusion, Synovial thickening or enhancement in MRI	Fibrosis of the deeper dermis and hyalinization of collagen bundles	Serologic tests	Erythema migrans
	Crystal-induced arthritis	Gout	+	+/-	-	-	-	+	Local swelling and erythema	Leukocytosis	↑	Needle shaped urate crystals, WBC count > 2000/µL	Urinary uric acid (>1100 mg in 24h)	Punched-out erosions or lyticareas with overhanging edges	Complementary for recognizing erosions	Tophi or edema in MRI	Large pale pink acellular areas (urate crystals), surrounded by histiocytes and multinucleated giant cells	Synovial fluid microscopy	Conjunctival nodules
		Pseudo-gout	+	-	-	-	-	+/-	Local swelling and erythema	Leukocytosis	↑	Rod shaped CPPD crystals, WBC count > 2000/µL	Hypercalcemia, Hypercalciuria	Radiodense lines paralleling the articular surface and calcification (chondrocalcinosis)	Calcific mass with a lobulated configuration in the ligamentum flavum or the joint capsule	Synovitis and calcific deposits in ultrasonography	Synovial calcium pyrophosphate crystals	Synovial fluid microscopy	Tenderness
	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	+	+	+	+/-	-	-	Petechia and purpura	Anemia, Leukocytosis, Thrombocytopenia	↑	WBC count >2000/µL (inflammatory), with neutrophilpredominance	LDH, Uric acid	Articular surface erosion, Synovial effusion	Thickened synovium	Synovitis in MRI	Inflammatory cells infiltration in synovial tissue	Bone marrow biopsy	Fatigue, Nausea, Recurrent infections