BACKGROUND: Long-term results of Genesis I modular total knee system are not well known.METHODS: We analyzed data from 345 patients with 393 primary total knee arthroplasties (TKA) using the Genesis I prosthesis. In all cases, the posterior cruciate ligament (PCL) was retained, and the patella was not resurfaced. The minimum follow-up was 10 (range 10-16) years.RESULTS: Preoperative range of motion improved from 89° preoperatively to 105° at the time of the most recent follow-up (p < 0.001). Mean preoperative Knee Society pain and function scores increased from 29 and 25 points to 91 and 85 points, respectively (p < 0.001). Tibiofemoral angle shifted from 2.40° of varus before to 4.8° of valgus after the operation (p < 0.001). Early postoperative complications occurred in 34 knees (8.6%). Manipulation under general anesthesia was done in six knees (1.5%). Nonprogressive radiolucent lines were seen around the femoral component in 16 knees (4%) and at the tibial bone-cement interface in 101 knees (25%). However, in only five cases (1.3%) was there significant progression leading to implant loosening and revision surgery. Eight more revisions were performed due to infection (three knees), stiffness (three knees), excessive wear and fracture of polyethylene liner (one knee), and instability (one knee). The overall survivorship of knee replacement reached 96.7%.CONCLUSIONS: In the long term (up to 16 years), PCL-retaining Genesis I total knee prosthesis is associated with good functional outcomes and low failure rates.