366 patients undergoing total knee arthroplasty were randomized to receive either a posterior knee capsule infiltration (iPACK) combined with an adductor canal block (ACB) (n=183) or a sham block (n=183). The primary outcome was postoperative pain scores. Secondary outcomes included opioid consumption, functional recovery (range of motion and quadriceps strength), and stress response measured by neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR). Outcomes were assessed up to 72 hours postoperatively. Overall, the iPACK + ACB group demonstrated significantly lower pain scores, reduced opioid consumption, improved knee range of motion, and decreased stress markers. The findings suggest that iPACK combined with ACB is effective for pain management, promoting functional recovery, and reducing surgical stress.