Background: Femoral 3-in-1 nerve block (FNB) alone is frequently used for pain control after total knee replacement (TKR), as the following nerves are inconsistently anesthetized during a Femoral three-in-one block i.e., the Lateral cutaneous nerve (LCN) of the thigh, the Femoral nerve (FN) and the anterior branch of the Obturator nerve (ON). But does not provide complete postoperative analgesia as the posterior branch of the Obturator nerve (ON) and femoral branch of the genitofemoral nerve are not blocked. The intact sensation in the back of the knee after an FNB alone could be attributable to either the obturator or the sciatic nerve, which also supplies the knee joint [