Total knee replacement (TKR) achieves an immediate and exceptional restoration in the quality of life that is comparable only to a few other procedures. It has been suggested that the most common cause of revision TKR is error in surgical technique, from malpositioning of the components which results in a poorer post-operative outcome. Based on the theoretical assumption that the use of computer-assisted systems (CAS) in TKRs may improve implant alignment and thus implant longevity, the use of this technology is becoming increasingly popular. This article (a) reviews whether computer-assisted TKR (CASTKR) results in improved prosthesis alignment compared with the conventional technique, (b) assesses the functional and clinical outcomes of CASTKR and (c) evaluates the cost-effectiveness of using this technology.