Morning stiffness precedes the development of RA and associates with systemic and subclinical joint inflammation in arthralgia patients.

OBJECTIVES Morning stiffness (MS) is characteristic for Rheumatoid Arthritis (RA) and associates with markers of systemic and local inflammation in RA-patients. In patients with arthralgia, MS is a cardinal symptom to recognize arthralgia at-risk for RA-development (i.e. clinically suspect arthralgia, CSA). In CSA, MS is also assumed to reflect inflammation, but this has never been studied. Therefore we aimed to study whether MS in CSA-patients is associated with systemic- and subclinical joint-inflammation. METHODS 575 patients presenting with CSA underwent laboratory investigations and contrast-enhanced 1.5 T-MRI of hand and forefoot (scored according to the RAMRIS-method). Associations of MS (duration ≥60 min) with presence of subclinical joint-inflammation (synovitis, tenosynovitis and osteitis) and increased-CRP (≥ 5 mg/l) were determined with logistic regression. Additionally, the effect of MS-duration (≥30, ≥60, ≥120 min) was studied. RESULTS 195 (34%) CSA-patients experienced MS. These patients more often had subclinical synovitis (34% vs 21%, OR 1.95 (95%CI 1.32-2.87)), subclinical tenosynovitis (36% vs 26%, OR 1.59 (1.10-2.31)) and increased-CRP (31% vs 19%, OR 1.93 (1.30-2.88)) than patients without MS. In multivariable analyses, subclinical synovitis (OR 1.77 (1.16-2.69)) and CRP (OR 1.78 (1.17-2.69)) remained independently associated with MS. In CSA-patients who later developed RA, and thus in retrospect were 'pre-RA' at time of CSA, MS was more strongly associated with subclinical synovitis (OR 2.56 (1.04-6.52)) and CRP (OR 3.86 (1.45-10.24)). Furthermore, associations increased with longer MS-durations. CONCLUSION Inflammation indeed associates with MS, already in the CSA-phase that preceded clinical arthritis. These results increase understanding of MS when assessing arthralgia in clinical practice.