Clement ND, et al. - A Markov decision analysis was done in order to conduct an analysis to determine the cost per quality-adjusted life-year (QALY) of robot-assisted unicompartmental knee arthroplasty (rUKA) in regards to manual TKA and unicompartmental knee arthroplasty (UKA) for patients with isolated medial compartment osteoarthritis (OA) of the knee and to evaluate how case volume and length of hospital stay impacted the relative cost per QALY. Using a model with an annual case volume of 100 patients, in relation to TKA and UKA, the cost per QALY of rUKA was £1,395 and £1,170, respectively. The cost per QALY was impacted by case volume, ie, a low-volume centre performing ten cases per year would attain a cost per QALY of £7,170 and £8,604 in relation to TKA and UKA. For a high-volume centre performing 200 rUKAs per year with a mean two-day length of stay, the cost per QALY would be £648 and if done as day-cases, the cost would be decreased to £364 in regards to TKA. The cost per QALY would be £574 for a high-volume centre performing 200 rUKAs per year with a shorter length of stay of one day in relation to manual UKA. Thus, for patients with isolated medial compartment OA of the knee, rUKA is a cost-efficient alternative to manual TKA and UKA. The cost per QALY of rUKA reduced with decreasing length of hospital stay and with rising case volume, in comparison with TKA and UKA.