200 knee arthroplasty patients were randomized to three groups: single-injection Femoral Nerve Block (FNB), continuous FNB, or Patient Controlled Analgesia (PCA) to compare the analgesic effects of single-injection and continuous femoral nerve blocks (FNB) with intravenous PCA opioids. After 3 months of post-operative evaluation, both methods of FNB significantly reduced knee pain at movement, improved knee flexion, and lowered opioid consumption compared to PCA, with continuous FNB showing superior outcomes and fewer side effects of vomiting and nausea.