The aim of this study was to determine the outcomes and survivorship of the Triathlon knee replacement at 7 years after surgery. A cohort of 266 patients receiving a Triathlon knee replacement were assessed before surgery and at 3 months, 1 year, 2 years, 3 years, 5 years and 7 years post-operation. Patient-reported outcomes were assessed using the WOMAC, KOOS Knee-Related Quality of Life scale, Satisfaction Scale and questions on kneeling ability and whether they regretted having the operation. Data on survivorship was collected from self-report and medical records. At 7 years after surgery, 32 patients were deceased, and 17 patients were withdrawn. Of the 217 patients remaining in the study, 164 (76%) returned a completed study questionnaire. At 7 years after surgery, 92% of patients reported an improvement in their WOMAC Pain score greater than the minimally clinically important improvement (defined as improvement of ≥9 points from before surgery) and 82% reported this in their WOMAC Function score (defined as improvement of ≥12 points). Knee-related quality of life was good, with a mean score of 66.8 (SD 26.0) (0–100 scale, worst to best). A high percentage of patients (89%) were somewhat or very satisfied with their outcome at 7 years. Survivorship with revision as the endpoint was 96.4% (95% CI 93.2–98.1%) at 7 years post-operation. Five percent of patients regretted having their operation and 68% reported much difficulty or an inability to kneel. In conclusion, this study observed good long-term patient outcomes and survivorship of the Triathlon knee replacement.