Optimal Treatment Interval of Viscosupplementation for Osteoarthritic Knee Pain: Real-world Evidence from a Retrospective Study

Abstract

Background: The evidence supporting multiple courses of viscosupplementation for knee osteoarthritis continues to grow; however, the optimal treatment interval for repeat courses is not well understood. To address this, we compared baseline pain and disability scores in patients returning for subsequent treatment with their prior discharge scores. Methods: We retrospectively collected data from patients at 16 rehabilitation clinics who presented for repeated courses of viscosupplementation treatment for knee OA. Primary outcomes were pain (visual analog scale, VAS) and Western Ontario and McMaster Universities Arthritis Index (WOMAC) scores, which were collected following the initial treatment course and compared with scores upon return for treatment. The proportion of patients who fulfilled a minimal clinically important difference in each outcome was calculated. Results: 61 patients (81 knees) were included in our analysis. After a 6-month treatment interval, no significant differences were noted between post-discharge and returning scores for either VAS (p=0.73) or WOMAC (Pain: p=0.42; Function: p=0.54; Stiffness: p=0.29). Patients waiting 9 months to return for treatment saw a 45% increase in their pain scores (p=0.10) and significant worsening in WOMAC scores (Pain: p=0.007; Function: p=0.03; Stiffness: p=0.04). At 12 months, pain (p=0.01), WOMAC Pain (p=0.05), and WOMAC Stiffness (p=0.02) had all worsened significantly compared to discharge following the initial course. Conclusion: Our data indicate that patients who return for treatment within a 6-month treatment interval maintain their improvements, but that when the interval increases to 9 months or more, patients present as significantly worsened, having lost the benefit of their initial course of treatment.