Total knee arthroplasty systems are continually being updated. Evaluating these new systems for their effectiveness, and potential complications is vital, and is closely monitored by the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). The ATTUNE Knee System was released in 2013, and some early studies reported on an increase in rates of aseptic loosening. This study aims to investigate the revision rates of the ATTUNE Knee System and its predecessor the PFC Sigma utilizing registry data. Data were collected from AOANJRR. All ATTUNE and PFC Sigma primary total knee replacements (TKR) performed between September 1999 until 2021 were included. The primary outcome measures were revision rates and indications for revision. A total of 38,407 primary TKRs were included in the study (24,863 ATTUNE, 13,544 PFC Sigma). The cumulative percentage revision (CPR) at 8 years was 3.3% (95% confidence interval [CI]: 2.6, 4.1) for the ATTUNE Knee System and 3.2% (95% CI: 2.9, 3.5) for the PFC Sigma Knee System (p = 0.144). The proportion of revisions due to aseptic loosening was 20.5% for the ATTUNE Knee System and 21.5% for the PFC Sigma Knee System. Midterm revision rates of the ATTUNE and PFC Sigma Knee Systems are not significantly different. Additionally, the percentage of revisions due to aseptic loosening of the implant were not significantly different between the two knee systems.