Introduction Total knee arthroplasty (TKA) is the definitive surgical treatment for advanced gonarthrosis when conservative measures fail. Among the available implant designs, posterior cruciate-retaining (PCR) and posterior-stabilized (PS) prostheses are widely used, yet their comparative performance in long-term functional recovery and health-related quality of life remains under debate. Methods We conducted a prospective observational study involving 48 elderly patients undergoing primary TKA at a tertiary-care center in Mexico. Participants received either PCR (n=27) or PS (n=21) implants based on intraoperative assessment. Patient-reported outcomes were evaluated using the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) Index, the 36-Item Short Form Health Survey (SF-36), and Patient-Reported Outcomes Measurement Information System (PROMIS-10) Global Health questionnaire at preoperative, six, 12, and 24 months postoperatively. Results Both groups demonstrated improvements in all outcome measures; however, PCR patients consistently achieved better results across the follow-up period. At 24 months, WOMAC scores, which reflect better symptom control with higher values, were superior in the PCR group for pain (77.5 vs. 71.0), stiffness (72.5 vs. 62.5), and physical function (86.5 vs. 82.6). SF-36 also favored PCR in physical functioning (66.5 vs. 64.1), bodily pain (72.1 vs. 70.0), and role-physical (54.0 vs. 51.0). PROMIS-10 confirmed these trends, with higher physical (73.9 vs. 71.3) and mental health scores (75.2 vs. 72.0) among PCR patients at 24 months. Conclusions Patients receiving cruciate-retaining prostheses experienced greater and more sustained improvements in pain relief, joint function, and quality of life compared to those with posterior-stabilized implants. These findings support the functional advantage of PCR designs in elderly patients undergoing TKA and highlight the value of long-term, multidimensional outcome assessment using patient-reported outcome measures (PROMs).