1945: Significance of Finger Joint Tenderness With or Without Swelling in Relation to MRI, Ultrasound, and X-Ray Findings in Psoriatic Arthritis_Final results

Background/Purpose: Musculoskeletal involvement in psoriatic arthritis (PsA) affects both articular and extra-articular structures, presenting as inflammatory and structural lesions. The relationship between tender and/or swollen joints and these lesions on imaging is not fully defined.

Purpose: To assess the clinical significance of tender-only (TJ+/SJ−) finger joints in PsA, compared to tender and swollen joints (TJ+/SJ+), in relation to inflammatory and structural lesions on MRI, ultrasound (US), and X-ray, and to evaluate the added diagnostic value of imaging.

Methods: This prospective study included 100 consecutive PsA patients (CASPAR criteria) with finger joint involvement. Physical exam categories were: tender and swollen joints (TJ+/SJ+), tender only (TJ+/SJ−), and normal joints (TJ−/SJ−). Swollen-only joints (TJ−/SJ+) were excluded due to small numbers (n=3). On the day of clinical evaluation, all patients underwent US (gray scale and Doppler) of 14 finger joints on the symptomatic hand (MCP I–V, IP, PIP II–V, DIP I–V), assessing synovitis, flexor tenosynovitis, extensor peritenonitis, erosions, and bone proliferation per EULAR-OMERACT. Within 3 days, MRI of the hand was performed, assessing the same lesions plus bone marrow edema (BME) and periarticular inflammation using PsAMRIS. Seventy patients completed hand X-rays within 1 month, scored by PsA Ratingen Score. Imaging assessors were blinded to clinical findings.

Results: Mean age was 51.2±12.6 years, 59% were female, and mean PsA duration was 10.3±11.2 years. TJ+/SJ+ joints had the highest prevalence of inflammatory and structural lesions across all modalities. However, 28% (MRI) and 33% (US) of joints in this category showed no inflammatory lesions. TJ+/SJ− joints had a lower prevalence of findings but were more involved than TJ−/SJ− joints. Subclinical inflammation (in TJ−/SJ−) was rare. Agreement between TJ+/SJ+ and imaging findings ranged from slight to moderate (kappa 0.42–0.01), with highest values for synovitis. TJ+/SJ− showed lower agreement. Sensitivity and positive predictive value (PPV) of TJ+/SJ+ ranged from low (tenosynovitis) to moderate (synovitis), while specificity and negative predictive value (NPV) were high. TJ+/SJ− had low sensitivity and PPV but high specificity and NPV. MCP, PIP, and DIP joint-level analyses showed similar trends.

Conclusion: Tender and swollen joints (TJ+/SJ+) were associated with the highest prevalence of imaging-detected inflammatory lesions. However, a considerable proportion of these joints did not show active inflammation on MRI or US, highlighting the limited positive predictive value of physical examination. Tender-only joints (TJ+/SJ−) demonstrated fewer imaging abnormalities but still had a higher prevalence of lesions than clinically inactive joints (TJ−/SJ−), indicating their intermediate diagnostic relevance. Importantly, subclinical inflammation in non-tender, non-swollen joints (TJ−/SJ−) was rare, reinforcing the utility of physical examination in ruling out active disease. These findings underscore the limitations of physical examination alone and support the integration of imaging into routine PsA assessment.