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Table 1 Ultrasound features used in differentiation of early inflammatory arthritis

From: The importance of ultrasound in identifying and differentiating patients with early inflammatory arthritis: a narrative review

Rheumatoid arthritis Spondyloarthritis Crystal arthropathies Polymyalgia rheumatica Septic arthritis
 • Joint effusion, synovial proliferation, synovial pannus, and hyperemia in typical RA distribution
 • Tenosynovial effusions, synovial hypertrophy, and hyperemia
 • Cortical bone erosions and cartilage lesions
 • Multijoint assessments confirming typical distribution of involvement
• Enthesitis characterized by tendon/ligament hypoechogenicity and thickening, calcification, bone erosions, intralesional focal calcification or fibrous tissue, and abnormal vascularization at enthesis insertion on power Doppler ultrasound
• Cortical bone erosions and enthesophytes (heterogeneous to RA)
• Synovitis and tenosynovitis
• Confounding factors: age, BMI
• Tophaceous deposits:
 • Cartilage: double contour sign (gout)
 • Periarticular: heterogeneous collection in soft tissue, “snowstorm” appearance sometimes with anechoic rim
 • Tendons and ligaments: intratendinous tophi and ovoid-shaped microdeposits with hyperechoic densities
• Cortical bone erosions
• CPPD deposits:
 • Hyaline cartilage: hyperechoic, within the layer of cartilage
 • Fibrocartilage: hyperechoic, rounded or amorphous deposits
• Basic calcium phosphate:
 • Hyperechoic foci with variable acoustic shadowing
 • Hyperemia on Doppler
• Bilateral subacromial/subdeltoid bursitis
• Biceps long-head tenosynovitis
• Trochanteric bursitis
• Synovitis
• Hip effusion
• Less common findings include enthesitis, glenohumeral effusions, flexor tenosynovitis, and peripheral synovitis
• Should not have hand- or wrist-joint synovitis
• Joint effusion, sometimes with hyperechogenicity and heterogeneity
• Increased peri-synovial vascularity with color Doppler
• Ultrasound can guide joint aspiration
• Clinical suspicion has the highest priority
  1. BMI body mass index, CPPD calcium pyrophosphate dehydrate, RA rheumatoid arthritis