Background/Purpose:  Extremity-MRI is becoming important in Rheumatoid Arthritis (RA) research as it is a sensitive tool to assess inflammation. Inflammation is measured by three features: bone marrow edema (inflammation of bone), synovitis and tenosynovitis. Part of the inflammatory lesions detected by MRI are subclinical, indicating that these were not observed by physical examination. The relevance of subclinical inflammation detected by MRI in a population of early arthritis patients for to the disease course is not known. In this study we investigated the relevance of subclinical inflammation on MRI in early arthritis patients for  radiological joint damage.

Methods:  179 early arthritis patients (median symptom duration of 15 weeks) included in the Leiden Early Arthritis Clinic underwent a 68-tender and 66-swollen joint count (including MCP, wrist and MTP joints) and a 1.5T MRI of the MCP (2-4), wrist and MTP (1-5) joints at the most painful side at baseline. Synovitis and bone marrow edema were scored according to the RAMRIS method; tenosynovitis at the wrists and MCP joints was also determined. Scoring was performed by two readers and the average scores were studied. Radiographs of hands and feet were made at baseline and after one year of follow-up and scored according to the Sharp-van-der-Heijde scoring method (SHS).

Results:  1,790 small joints of 179 patients were studied. Of these joints 1,525 (85%) were not swollen at physical examination. Of all clinically non-swollen joints, any subclinical inflammation was present on MRI in 25%; 15% had bone marrow edema, 15% synovitis and 18% tenosynovitis. When evaluating these clinically non-swollen joints in relation to the radiographs at year-1, 7% of the joints had SHS ≥1 and 2% SHS progression ≥1.

The subclinical inflamed joints were evaluated with progression of radiological joint damage over the first year (SHS progression ≥1) as outcome. When comparing the non-swollen joints with and without any inflammation on MRI, 4% versus 1% had SHS progression ≥1, (RR 3.5 (1.3-9.6)). For bone marrow edema this was 6.5% versus 1% (RR 5.3 (2.0-14.0), for synovitis this was 5% versus 1% (RR 3.4 (1.2-9.3)) and for tenosynovitis this was 4% versus 1% (RR 3.0 (0.7-12.7)). Hence, although radiological progression was infrequent, it was significantly increased in joints with subclinical synovitis or bone marrow edema. For comparison we studied the outcome of the swollen joints. 8% of all swollen joints had SHS progression ≥1 over the first year, indicating that the frequency of progression in subclinical inflamed joints almost equaled the frequency of progression in clinically swollen joints.

Conclusion:  Joints with subclinical inflammation detected by MRI have an increased risk of progression in structural damage in early arthritis. This points to the relevance of subclinical inflammation for the disease outcome in RA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/radiological-outcome-of-joints-with-mri-detected-subclinical-inflammation-in-early-arthritis-patients/