Intra-articular injection of high versus low molecular weight hyaluronic acid in adhesive capsulitis; randomized trial.

BACKGROUND: Adhesive capsulitis (AC) is a chronic inflammatory condition with limited range of motion (ROM) in the glenohumeral joint. The main goals in managing AC are pain reduction and returning joint function. Intra-articular hyaluronic acid (HA) has been considered a safe modality in AC. This study compared the effectiveness of intra-articular injection of low molecular weight (LMW) with high molecular weight (HMW) HA in patients with AC. METHODS: Fifty-six patients with AC were randomized in this triple-blinded clinical trial. All underwent standard physical therapy. The outcomes were visual analog scale (VAS), Oxford shoulder score (OSS), active ROM, and patient satisfaction at 4, 12, and 24 weeks. RESULTS: No significant differences were detected in between-group variables at baseline. Both groups showed marked improvement in VAS, OSS, and ROM over time. At four weeks LMW-HA group had lower pain (P = 0.049). Conversely, the trend of VAS at 12-week and 24-week endpoints favors HMW-HA (Baseline to endpoint: -5.48 ± 1.68 and -3.91 ± 1.31 reduction in VAS as the primary outcome, P < 0.001). Satisfaction had significantly improved in both groups. CONCLUSION: HMW-HA was associated with greater pain reduction and functional improvement compared with LMW-HA. TRIAL REGISTRATION: The trial protocol was registered at the Iranian Registry of Clinical Trials (IRCT), a WHO Primary Register setup (registration No: IRCT20170608034390N4; First registration date: 01/01/2020).