One hundred fifty patients with symptomatic rhizarthrosis were randomized to receive a single ultrasound-guided intra-articular injection of corticosteroid (CS) + intra-articular hyaluronic acid (HA) (n=73) or CS+saline (n=76). The primary outcome was change in activity-related thumb pain (0–10 VAS) at 3 months (M3). Secondary outcomes included VAS at activity and rest at M1/M6/M12, Cochin hand function, grip/opposition strength, sonography at M3, and adverse events; follow-up was at 1, 3, 6, and 12 months. Overall, the results revealed greater pain reduction with CS+HA at M3, with a smaller early advantage at M1 that was not maintained at M6 or M12; other secondary endpoints showed no statistically significant between-group differences. These findings suggest that adding HA to CS yields a clinically meaningful but time-limited improvement in activity pain through 3 months.