Joint involvement patterns in oligoarticular JIA: Key determinants of prognosis

Oligoarticular juvenile idiopathic arthritis (oJIA) is the most common JIA subtype, with variable disease courses influencing long-term outcomes. Joint involvement patterns significantly affect disease activity, treatment response, and prognosis. This study evaluates the impact of joint involvement on disease activity, inflammatory markers, treatment needs, and disease extension in patients with oJIA. We retrospectively analysed 124 oJIA patients followed for a median of 62 months. Joint involvement, disease activity (Juvenile Arthritis Disease Activity Score [JADAS-27]), inflammatory markers (erythrocyte sedimentation rate [ESR], C-reactive protein [CRP]), and treatment modalities were assessed. Persistent and extended disease courses were compared. A total of 124 patients with oJIA (63.7% female) were included, with a median age at diagnosis of 8.2 years. The knee was the most frequently involved joint (87.1%), followed by the ankle (41.1%) and hip (22.6%). Patients with ankle, wrist, and elbow involvement had significantly higher JADAS-27 scores at baseline. Notably, ankle involvement was associated with sustained higher disease activity up to the first year and higher final CRP levels. Repeated measures ANOVA demonstrated a significant decline in JADAS-27 over time across all joint subgroups (p<0.001), with no joint-specific difference in trajectory. Ankle and small hand joint (MCP/PIP) involvement were significantly associated with increased use of cDMARDs and anti-TNF agents. Patients with extended oJIA had significantly higher JADAS-27 scores at all timepoints except the final visit and were more likely to have symmetric joint involvement and receive biologic therapy compared to those with persistent oJIA (anti-TNF use: 70% vs. 25%, p<0.001). Joint involvement patterns, particularly affecting the ankle, wrist, and small hand joints, are associated with higher disease activity and increased treatment requirements in oJIA. Symmetrical and extended disease forms further indicate a more severe course. Early identification of these high-risk features may guide personalized treatment and improve long-term outcomes.