Summary Unicompartmental knee replacement (UKR) or arthroplasty (UKA) has undergone a resurgence of interest and usage in recent years. This is partly due to the development of minimally invasive surgery (MIS) techniques for UKR. Many experienced arthroplasty surgeons correctly consider that UKR is more technically demanding than total knee replacement (TKR). However, in appropriately selected patients and with carefully performed surgery, the known benefits of UKR can be safely offered. Many previously learned lessons have had to be rediscovered to enable this technically demanding procedure. MIS has been demanded by patients and offered by surgeons but the limited surgical access makes the technical intricacy of UKR surgery even more demanding. Computer aided surgery (CAS) has emerged as a probable solution to this problem. This article examines the current place of UKR in arthroplasty surgery with particular reference to the new techniques of MIS and CAS. UKR has an important place in the selection of surgical options for the treatment of unicompartmental knee arthritis because of the rapid recovery, lower complication rate and high success rate compared to other available procedures.