The effect of unicompartmental knee arthroplasty on patellofemoral alignment

Abstract Patellofemoral pain syndrome is a clinical entity characterized by anterior knee pain, often arising from a complex interplay of factors including malalignment, periarticular muscle dysfunction, and osteoarthritis. Unicompartmental knee arthroplasty (UKA) has emerged as an effective treatment option for medial compartmental osteoarthritis, particularly in middle-aged and older patients, when patient selection criteria are carefully met. This retrospective study aimed to evaluate the impact of UKA on clinical outcomes and patellofemoral alignment in patients who underwent cemented Oxford Phase 3 UKA. Specifically, we assessed changes in patellofemoral alignment in the coronal, sagittal, and axial planes. Materials and Methods: A retrospective study was conducted on 44 patients who underwent unicompartmental knee arthroplasty at our institution between January 2016 and December 2022. The mean follow-up period was 28.8 months. Patient demographics included a mean age of 58.43±7.37 years and a mean body mass index of 28.55±3.18 kg/m². Results: Preoperative Oxford Knee Score (55.27) improved significantly postoperatively (81.59, p=0.000). Similar improvements were observed in Knee Society Score (13.57 vs. 37.32, p=0.000) and Kujala score (55.14 vs. 71.77, p=0.000). Patellar tilt angle decreased significantly from 12.58° to 9.98° (p<0.000). While Insall-Salvati ratio, patellar tilt, and lateral patellar displacement did not change significantly, MPTA increased from 84.80° to 87.21° (p=0.000), and HKA decreased from 7.64° to 2.39° (p=0.000) postoperatively. Conclusion: This study demonstrated that unicompartmental knee arthroplasty not only effectively corrected knee alignment and improved clinical and functional outcomes but also had a positive impact on patellofemoral region problems, thereby preserving normal gait mechanics.