Objective: Bone marrow oedema (BMO) and HLA-B27 are poor prognostic factors in axial SpA, and psoriasis is a poor prognostic factor in small-joint polyarthropathy. The aim of this study was to investigate the influence of HLA-B27, MRI BMO and psoriasis on long-term outcomes in early SpA-related knee joint oligoarthritis.
Methods: Patients with SpA-related oligoarthritis with knee involvement were recruited. Baseline assessment included ESSG criteria, RF, HLA-B27 and MRI. The degree of MRI BMO was determined on fat-suppression sequences and scored using the whole-organ magnetic resonance imaging score (WORMS) (range 0-45). Patients were treated at the discretion of their rheumatologist and followed up for 10 years. Outcome assessments included joint counts, functional and symptomatic questionnaire, CRP and radiographic assessment for OA.
Results: Forty-four patients were recruited [mean age 32 years (range 15-59 years), 70% male] with a mean disease duration at baseline of 9.75 months (1-48 months). Twenty-six (59%) patients (mean age 43 years, 65% male) returned for follow-up after a mean of 10 years (range 8.4-12.6 years). Ten (38%) patients had persistent clinical synovitis and 31% of knees had secondary radiographic OA. Global outcome was poor/very poor in 69% of cases. The only factor predicting outcome at 10 years was psoriasis, but neither HLA-B27 nor BMO. PsA patients had significantly worse global outcome compared with ReA (P = 0.036), and significantly worse symptomatic (P = 0.001) and functional (P = 0.001) outcome compared with other subtypes.
Conclusion: SpA-related knee joint oligoarthritis has significant long-term clinical and radiological morbidity despite standard treatments. HLA-B27 and MRI BMO were not predictors of poor outcome as they are in axial SpA; however, the presence of psoriasis predicted significantly worse outcome.