Preoperative patellofemoral malalignment weakened the outcome of patients after total knee arthroplasty.

Introduction: The impact of preoperative patellofemoral malalignment (PFM) on the prognosis of patients who underwent total knee arthroplasty (TKA) remains unknown. This study aimed to explore the effect of preoperative PFM on the prognosis of patients who underwent TKA.

Methods: This retrospective observational study included patients who underwent TKA at the Second Hospital Affiliated to Fujian Medical University between February 2018 and July 2020. The primary outcome measure was the Hospital for Special Surgery Knee-Rating Scale (HSS) score. The secondary outcomes included postoperative radiographic parameters (X-rays) and the occurrence of complications.

Result: A total of 94 patients (107 knees) who underwent TKA were included in the study. Of these, 37 knees had PFM and 70 had normal patellofemoral alignment (PFA). Patients with preoperative PFM showed a change in patellar outward displacement from 7.01 ± 3.91 mm preoperatively to -0.31 ± 2.86 mm postoperatively (p<0.001), and the lateral patellar tilt angle changed from 9.45 ± 7.47° to 6.06 ± 3.61° (P=0.009). Postoperative radiographic parameters between the PFM and PFA groups did not show any significant difference (p>0.05), but the postoperative HSS score in the PFM group was lower than in the PFA group (total score: 70.35 ± 8.39 vs. 80.47 ± 5.44, p<0.001). In addition, 13 (35.14%) knees in the PFM group experienced postoperative anterior knee pain compared to 10 (14.29%) knees in the PFA group (P=0.013).

Conclusion: Preoperative PFM may have an impact on the HSS score and the occurrence of anterior knee pain in patients after TKA. These findings suggest that surgeons should carefully evaluate preoperative PFA in patients undergoing TKA. Furthermore, patients with PFM may require additional monitoring and management of postoperative anterior knee pain, as well as special considerations for optimizing functional outcomes.