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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:

To review the differential diagnosis of monoarthritis with joint swelling, click here.

To review the differential diagnosis of monoarthritis with fever, click here.

To review the differential diagnosis of monoarthritis with weight loss, click here.

To review the differential diagnosis of monoarthritis with claudication, click here.

To review the differential diagnosis of monoarthritis with morning stiffness, click here.

To review the differential diagnosis of monoarthritis with local erythema, click here.

To review the differential diagnosis of monoarthritis with joint swelling and fever, click here.

To review the differential diagnosis of monoarthritis with joint swelling, fever, and weight loss, click here.

Diseases Clinical manifestations 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[1] + - - - - - 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[2] + - - - - + Wound or laceration - - Hemarthrosis - Severe joint effusion, Fracture Fracture, Synovial tear - - X-ray Deformity, Severe pain
Neoplasms[3] + - + +/- - - 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
Infectious Arthritis Gonococcal Arthritis[4] + + - - - + 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) DermatitisTenosynovitis
Nongonococcal Arthritis[5] + + - - - + 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
Pott's Disease[6] - + + + +/- - 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 Joint Infection[7] - +/- - - - +/- 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 Arthritis[8] + + +/- +/- - - 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[9] + +/- - - - + 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[10] + - - - - +/- 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[11] +/- +/- - - - - 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 ConjunctivitisUveitis
Psoriatic arthritis[12] + - - - - + Scaly erythematous plaques,

Guttate lesions, Lakes of pus,


Normal High WBC count (5000-15,000/µL) with >50% of PMN leukocytes RFANAIgA Joint-space narrowing, Fluffy periostitis Pencil-in-cup deformity, Early signs of synovitis Sacroiliitic synovitisEnthesitis in MRI Lack of intrasynovial Igand RF, Greater propensity for fibrous ankylosisosseous resorption, and heterotopic bone formation Clinical findings OnycholysisSplinter hemorrhages
Inflammatory bowel disease-associated arthritis[13] + + - - + +/- Pyoderma gangrenosum(ulcerative colitis),Erythema nodosum(Crohn disease) Iron deficiency anemiaLeukocytosisThrombocytosis Mild to moderate inflammatory fluidPMNpredominance RFAntiendomysial 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[14] + - - - - - 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 blockOcular lesion
Rheumatoid arthritis[15] + - + + + - Rheumatoid nodules AnemiaThrombocytosis WBC count >2000/µL (generally 5000-50,000/µL), with neutrophilpredominance (60-80%) Anti-CCP AbHyperuricemia 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[16] + + + +/- - - Petechia and purpura Anemia,



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


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