“…The disease states which were defined by OA severity include: normal radiograph (no OA), questionable osteophytes (preradiographic OA), definite osteophytes (early OA), <50% narrowing of knee joint space (advanced OA), and ≥50% narrowing of joint space (end-stage OA). A decision-analytic model in the form of a decision tree was used to evaluate the cost-effectiveness of hydrotherapy vs land-based therapy; the model duration was set as 3 months [17]. The third study that evaluated the cost-effectiveness and cost-utility of tele-rehabilitation adopted a Markov model and the cycle length considered was 1 year [19].…”