Sternoclavicular joint (SCJ) involvement in psoriatic arthritis (PsA) is poorly characterized. We aimed to assess its prevalence and clinical associations in a longitudinal PsA cohort. We retrospectively analyzed prospectively collected data from the Gladman Krembil Psoriatic Arthritis Program. Patients with SCJ involvement (tender and/or swollen SCJ) were identified, and their demographic, clinical, laboratory, and treatment details were retrieved. Univariable and multivariable generalized estimating equation models were used to assess associations with clinically swollen SCJ. Results are reported as odds ratios (OR) with 95% confidence intervals (CI). Among 1,737 patients, 182 (10.5%) had SCJ involvement, including 36 (2.1%) with clinically swollen SCJs ever over follow-up. SCJ involvement was present at enrolment into the cohort (baseline) in 33.1% of affected individuals. The mean age was 41.4 ± 12 years, and 42% were male. In univariable analyses, SCJ involvement was significantly associated with higher swollen joint count (SJC) (OR 1.142, 95% CI 1.08-1.16), dactylitis (4.51, 2.02-10.05), and enthesitis (6.74, 3.45-13.15). No significant associations were observed with sex, disease duration, axial and nail disease, PASI, pustular psoriasis, or HLA markers. In multivariable analysis, SCJ swelling remained associated with higher SJC (1.08, 1.03-1.14), enthesitis (4.54, 1.98-10.45), dactylitis (4.54, 1.98-10.45) and lower biologic or targeted synthetic DMARD use (0.30, 0.10-0.88). SCJ involvement is an underrecognized but clinically meaningful manifestation of PsA, associated with greater disease burden and enthesitis, often requiring escalation to advanced therapies.
