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Background Aim of this study was to compare functional results within 36 months following primary total knee arthroplasty (TKA) using a conventional prosthesis Multigen Plus CR and a new Physica KR implant. Our hypothesis was that the use of the Kinematics-Retaining design of an TKA implant leads to a significantly greater improvement in the active range of motion and better functional results (KSS 1, KSS 2 and WOMAC score) than the conventional CR implant at short-term follow-up. Materials and methods We retrospectively analysed data of 234 patients who underwent primary TKA at our hospital from April 2010 to August 2015 with the CR type of implant and from July 2014 to August 2015 with the KR implant due to advanced knee arthrosis of IIIrd and IVth grade of Kellgren-Lawrence classification, with no major ligamentous instability. Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) questionnaire, Knee Society Scores 1 (KSS 1) and 2 (KSS 2) and flexion (AROM) were recorded preoperatively and at 6, 12 and 36 months after surgery. Results Our study showed a statistically significant difference in functional results at three years with better KSS 1 score, a tendency to higher values in the KSS 2 score, as well as a statistically significant overall improvement in AROM in favour of the new KR design over the conventional CR implant with a post-hoc power analysis of 83.8%. We found that there was no statistically significant difference between groups when comparing WOMAC score and complications at short-term follow-up. Conclusions Our study provided more favourable clinical results for using Kinematics-Retaining implant in primary TKA. Further studies should focus on radiological and functional outcomes from mid- to long-term follow-up.