Introduction: Unicompartmental knee arthroplasty (UKA) can be used to treat medial compartment osteoarthritis of the knee. Some of these knees will eventually fail, and need to be revised. There is controversy about using UKA in younger patients as a definitive procedure or as a means to delay total knee arthroplasty (TKA) because the outcomes of subsequent revision surgery may be inferior to a primary TKA.Methods: We retrospectively reviewed a series of 46 revision TKA patients following failed UKA (UKA revisions) using functional outcomes questionnaires and compared the results with a cohort of age and gender matched primary TKA patients. Our hypothesis was that UKA revision surgery would be inferior to primary TKA surgery.Results: Data was collected on 33 knees after a mean follow-up period of five years. There was no significant difference in the Oxford Knee Score (33.7 vs 37.1, p = 0.09) or the Western Ontario and MacMasters Universities Arthritis Index (WOMAC) (24.8 vs. 19.1, p = 0.22). A subgroup analysis demonstrated that UKAs, which fail early, are more likely to produce an inferior outcome following revision surgery than those that survive more than five years.Discussion: We conclude that UKA can be used effectively in appropriately selected patients, as the functional outcome of their subsequent revision to TKA is not significantly inferior to a primary TKA.