['To assess the impact of different subsets of symptomatic hand osteoarthritis (OA) on pain and disability.', 'From 308 patients with hand OA a group with carpometacarpal joint (CMCJ) symptoms only (group I, n=20) was identified as well as groups with symptoms at the interphalangeal joints (IPJs) only (group II, n=138), and symptoms at both sites (group III, n=150). Hand pain and function, assessed with the AUSCAN, were compared between groups using linear mixed models. Radiological OA was assessed using the Kellgren-Lawrence grading scale.', 'Mean (SD) AUSCAN scores for groups I, II and III were 23.1 (11.7), 18.3 (11.9) and 26.4 (12.5), respectively. After adjustment for age, gender, body mass index, family effects and number of symptomatic hand joints, significant differences in AUSCAN scores of 7.4 (95% CI 1.8 to 13.0) between groups I and II, and 5.7 (95% CI 2.7 to 8.6) between groups II and III were found. AUSCAN scores were 5.8 (95% CI 3.1 to 8.6) higher for patients with versus patients without CMCJ symptoms. Kellgren-Lawrence scores did not differ between groups.'] Is thumb base involvement in symptomatic hand osteoarthritis associated with more pain and functional disability?