Background: Glenohumeral osteoarthritis (GH OA) is a very common joint disease characterized by pain and functional limitation. No standardized protocols of treatment are available in clinical practice and literature data are confusing. This monocentric randomized open-label study aims to assess the efficacy and safety of a treatment with medium molecular weight Hyaluronic Acid (HA) compared to a treatment with corticosteroids on patients affected by glenohumeral osteoarthritis.Methods: A total of 80 consecutive patients with GH OA (Kellegren Lawrence grade II or III) were randomized in two different groups: Hymovis (R) (24 mg/3 mL) (treatment group) and corticosteroids (control group), with a follow-up after 3 and 6 months. Modifications in terms of pain, range of motion and quality of life were observed during the treatment.Results: After 6 months, the treatment group presented a mean active abduction (ABD) of 67.9 degrees +/- 3.6 (baseline 56.4 degrees +/- 4.5, a gain of 11.5 degrees), the mean internal rotation (INT) was 14.4 degrees +/- 2.0 (baseline 13.6 degrees +/- 2.1. a gain of 0.8 degrees) and the mean external rotation (EXT) was 24.3 degrees +/- 2.5 (baseline 23.5 degrees +/- 2.9, a gain of 0.8 degrees) for patients belonging to the treatment group. The mean Constant-Murley Score (CMS) in the treatment group was 76.5 +/- 4.3 (baseline 59.5 +/- 5.4, a gain of 17.0 from the starting point). The mean Visual Analogue Scale (VAS) was 4.6 +/- 0.7 (baseline 8.0 +/- 1.1, a reduction of 3.4), and the EuroQol-5 Dimension (EQ-5D) was 70.6 +/- 4.3 (baseline 53.7 +/- 5.1, a gain of 16.9). For patients in the control group, after 6 months, the mean active ABD was 60.4 degrees +/- 4.8 (baseline 58.9 degrees +/- 4.8, a gain of 1.5 degrees), the mean INT was 15.3 degrees +/- 1.9 (baseline 14.9 degrees +/- 2.0, a gain of 0.4 degrees) and the mean EXT was 22.8 degrees +/- 2.1 (baseline 23.5 degrees +/- 2.9, a gain of 0.6 degrees). The mean CMS was 66.5 +/- 4.8 points, (baseline 61.2 +/- 4.7, a gain of 5.3). The mean VAS score was 7.2 +/- 1.1 (baseline 7.9 +/- 1.1, a reduction of 0.7), and the EQ-5D was 62.1 +/- 3.8 (baseline 54.9 +/- 4.7, a gain of 7.2). At 6 months follow-up, patients treated with HA showed a significant reduction in the level of pain and a significant improvement in their daily activities in comparison with the control group.Conclusion: The present study demonstrates that patients affected by mild-moderate GH OA treated with two intra-articular injections of HA (Hymovis (R) 24 mg/3 mL) achieved better results for a longer duration, in terms of reduction in shoulder pain and improvement in their daily activities, compared to patients treated with two intra-articular injections of corticosteroids.Clinical Trial Registration: No. NCT06043544. URL: https://clinicaltrials.gov/.