A Complete Infrapatellar Fat Pad Resection is Associated with New Postoperative Patella Baja and Persistent Pain, but a Lower Risk of Manipulation Under Anesthesia after Primary Total Knee Arthroplasty.

Abstract

Patella baja after total knee arthroplasty (TKA) is associated with postoperative stiffness, and there is conflicting evidence regarding the patellar fat as a source of pain. We hypothesized that a complete infrapatellar fat pad resection during primary TKA does not increase the incidence of new postoperative patella baja while reducing the incidence of persistent pain and improving postoperative function. Specifically, we evaluated the odds of 1) new patella baja, 2) persistent pain, 3) Knee Society Score (KSS), 4) range of motion, and 5) manipulation under anesthesia. The primary outcome of this single-institution retrospective study was the incidence of new patella baja comparing pre- and postoperative lateral knee radiographs using the Insall-Salvati ratio of patients who underwent a primary TKA with either a complete or partial infrapatellar fat pad resection from 2014 to 2025. The final cohort included 592 patients who had either a complete (n = 351) or partial (n = 241) infrapatellar fat pad resection. The secondary outcomes included KSS, persistent pain, and range of motion. Differences in outcomes between complete and partial fat pad resection were assessed via risk-adjusted multivariable binomial and linear regression models. A complete infrapatellar fat pad resection nearly tripled the odds of new patella baja compared to a partial resection [2.92 (confidence interval (CI): 1.12 to 9.15); P = 0.041; number needed to harm [NNH] = 26]. Complete resection also more than doubled the odds of persistent pain [2.45 (CI: 1.17 to 5.54); P = 0.022; NNH = 19]. The Knee Society scores (KSS) were lower by 2.9 (CI: 1.2 to 4.7) points with complete resection (P = 0.001). After adjustment, no differences were noted in the range of motion. Our study highlights that infrapatellar fat pad resection may be a potential risk factor for developing new patella baja and persistent pain after primary TKA.