Important Considerations When Determining the Cost-effectiveness of Viscosupplements in the Treatment of Knee Osteoarthritis: Letter to the Editor regarding Rosen, J., Sancheti, P., Fierlinger, A. et al. Adv Ther (2016) 33: 998. doi:10.1007/s12325-016-0331-8

The economic costs of knee osteoarthritis (OA) and its treatment are important considerations for patients, physicians, and healthcare systems when making decisions about the management of knee OA, especially given the direct costs associated with total knee replacement (TKR) [1, 2], and the estimated increase in demand by 2030 projected for TKR in the United States (673% increase from 2005 for primary TKR) [3]. Viscosupplementation has been shown to delay the time to TKR [4–6], making it an attractive option for delaying or reducing healthcare costs due to TKR. However, users of the treatment have a number of Food and Drug Administration (FDA)-approved viscosupplementation products with potentially different cost-benefit impacts from which to choose. These include, among others, The purpose of the study by Rosen et al. [7] was to indirectly evaluate the cost-effectiveness of different forms of intra-articular (IA) hyaluronic acid (HA) injections for the treatment of knee OA based on efficacy data that were extracted from a select set of randomized controlled trials and converted into utility scores. We have serious concerns regarding this approach, especially with some of the assumptions made by Rosen et al. [7] and in light of other available data not included in their analysis. Our concerns are outlined below. First, the study selection approach the authors employed did not result in adequate representation of available viscosupplementation treatments. They conducted a systematic search for randomized controlled trials that each examined the use of IA-HA in knee OA and reported full Western Ontario and McMaster Universities Index (WOMAC) pain, stiffness, and functional outcome data in a 5-point Likert format at both baseline and 6-month follow-up. Their search yielded just five articles with information on only five products [one article each for