Debate remains regarding the utility of mechanical axis alignment as a predictor of durability after total knee arthroplasty (TKA). Our study aimed to assess the effects of coronal alignment on implant durability, clinical outcomes, and radiographic results with a single fixed-bearing TKA design. All patients undergoing primary cemented TKA of a single design (Stryker Triathlon) from 2005-2007 with >10 years of follow-up and available pre-operative and post-operative hip-knee-ankle radiographs were included ( = 89). Radiographs were measured to determine coronal alignment and assessed for loosening. Mean preoperative mechanical axis alignment was -6° ± 6.7° (varus, range, -16°-23°), while mean post-operative alignment was -1° ± 2.7° (varus, range, -3°-15°). The aligned group was defined as knees with a post-operative mechanical axis of 0° ± 3° ( = 73) and the outlier group as those outside this range ( = 16). No patients underwent revision. Ten-year survivorship free from any reoperation was 99% and 100% in the aligned and outlier groups, respectively ( = 0.64). Knee Society scores improved significantly in both groups ( < 0.001) and did not differ at final follow-up ( = 0.15). No knees demonstrated radiographic evidence of loosening. Post-operative mechanical axis alignment within 3° of neutral was not associated with improved implant durability, clinical outcomes, or radiographic results at 10 years following primary TKA.