This retrospective study was designed to assess two fixed bearing total knee design concepts and their clinical outcomes, particularly in Forgotten Joint Score-12 (FJS-12). Patients were assessed clinically using the Knee Society Score (KSS). Participants completed an FJS-12 and a short form of the Knee Injury and Osteoarthritis Outcome Score (KOOS-PS). A total of 216 knees -76 with Genesis II and 150 with Vanguard total knee arthroplasties - were included. Patients in the Vanguard group had significantly better postoperative FJS-12 scores (by 10.1 points, p = 0.019). Differences in KSS subscores also reached the level of statistical significance. KOOS-PS did not differ significantly. Statistically significant differences between the two knee designs on FJS-12, KS and FS assessments were revealed, but overall, these differences may not reach the threshold of clinical significance.