Introduction: Correct alignment of prosthetic components is considered one of the most important factors for TKR (total knee replacement) survival. It is our aim, in this study, to determine the degree of correlation between measurements made by 2 observers and the assistant navigator during prosthetic knee surgery.

Materials and methods: In a total of 55 non-selected patients, operated with navigator assistance, two resident physicians in our Department, using a computer system measured, during the preoperative period, the ipsilateral and contralateral femorotibial axis, the femoral and tibial axis, and the inclination of the tibial plateau. They also measured, during the postoperative period, the tibiofemoral axis by means of digitalized X-rays. These measurements were compared with those made by the navigator.

Results: The degree of correlation between measurements was variable. The greatest degree of correlation between values was that of the preoperative tibiofemoral axis, with an r of: 0.83 (0.68–0.91 CI 95%) and the lowest degree of correlation was that of the measurements of the posterior tibial inclination.

Conclusions: A large number of axes and useful measurements have been described for the planning of reconstructive knee surgery, but since the introduction of new technologies applicable in this field, it is necessary to determine the degree of reliability and reproducibility of these so they can be correctly used by the orthopedic surgeon in their everyday clinical practice.