EC Orthopaedics

Synovitis is the fundamental pathological process in rheumatoid arthritis (RA), and accurate identification of active inflammation is central to diagnosis, prognostication, and treat-to-target therapeutic strategies. While musculoskeletal ultrasound (US), particularly with power Doppler (PD), and magnetic resonance imaging (MRI) provide sensitive assessment of synovial hypertrophy and vascularity, their cost, limited accessibility, and operator dependence restrict routine multijoint and serial evaluation. Infrared thermography (IRT), a non-contact imaging modality that detects cutaneous temperature variations, has re-emerged as a potential adjunctive tool for detecting inflammatory hyper perfusion associated with synovitis. Advances in sensor technology and portable devices have improved feasibility in both outpatient and remote settings. Recent clinical studies demonstrate consistent temperature differentials between inflamed and non-inflamed joints, with moderate correlations between thermographic indices and ultrasound-detected synovitis, particularly PD vascularity. Larger superficial joints such as the knee and elbow appear to show stronger concordance compared to smaller joints of the hand, where anatomical complexity and environmental influences may affect accuracy. The integration of automated image processing and machine-learning algorithms, including thermographic joint inflammation scores, has further enhanced reproducibility and enabled potential remote disease activity assessment. However, thermography remains an indirect measure of synovitis and is influenced by ambient conditions, patient-specific factors, and acquisition variability. The absence of standardized imaging protocols and limited multicentre validation currently preclude its use as a standalone diagnostic modality. Infrared thermography represents a promising, safe, and rapid adjunct for screening, monitoring, and triage in RA. Further large- scale prospective studies, standardized acquisition frameworks, and external validation of automated analytical models are required to establish its definitive clinical role.

 Keywords: Artificial Intelligence in Detecting Synovitis; Thermography in Rheumatoid Arthritis; Ultrasonography in Synovitis; Power Doppler in Synovitis of Small Joints

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