Eighty-two patients with primary adhesive capsulitis were randomized to hydrodilatation with corticosteroid (HDC; betamethasone 11.4 mg + lidocaine 2% + saline, total 20 mL; n=41) or hydrodilatation without corticosteroid (HDA; lidocaine 2% + saline, total 20 mL; n=41). The primary outcome was SPADI. Secondary outcomes included VAS pain, SST, and 12-month SSV. Outcomes were assessed at 48 hours (pain only), and at 1, 3, 6, and 12 months, with blinded evaluation and standardized rehabilitation for all. Overall, the results revealed that corticosteroid use produced faster and greater improvements: treatment effect was significant for SPADI (p=0.015) and VAS (p<0.001), and SSV at 12 months favored HDC (p=0.013). By 1–6 months, SPADI differences were clinically meaningful (≈13–16 points), persisting—though attenuated—at 12 months. In short, adding corticosteroid to hydrodilatation improved pain and function across follow-up.