Unicompartmental knee arthroplasty (UKA) is considered an excellent alternative to total knee arthroplasty (TKA) in the treatment of unicompartmental femoro-tibial degeneration with superior functional scores, reduced morbidity and fewer complications. However, revision rates are higher, mainly during the early postoperative period. Failures are attributed to incorrect indications, surgical technical errors and to the low threshold to revision. Several clinical and radiological parameters have to be considered for a correct indication. A high surgical volume is mandatory to assure optimal outcome and survivorship.