Total knee replacement (TKR) is associated with significant postoperative pain. This postoperative pain is difficult to treat with oral analgesics, resulting in adverse endocrine, metabolic, and inflammatory responses . Single-injection femoral nerve block (FNB) significantly improves postoperative analgesia compared with systemic opioid therapy at least during the first 24 hours after TKR or ACL reconstruction  although some studies show a limited benefit of single-injection FNB as an analgesic technique during TKR or ACL reconstruction. The pain after TKA is severe and does not fade noticeably for 48–72 h after the surgery. Effective pain control allows for earlier ambulation and initiation of physiotherapy, which hastens recovery, A reduces the length of stay in the hospital, and lowers the risk of postoperative complications, such as thromboembolic dis- ease or nosocomial infections. Bupivacaine is the standard, long-acting local anaesthetic used in regional anaesthetic practice together with ropivacaine, a N-propyl homologue of bupivacaine and a pure S(-) enantiomer . Ropivacaine has shown a reduced potential for central nervous system toxicity and cardiotoxicity in laboratory experiments and in healthy volunteers . Total knee replacement (TKR) is associated with significant postoperative pain. This postoperative pain is difficult to treat with oral analgesics, resulting in adverse endocrine, metabolic, and inflammatory responses . Single-injection femoral nerve block (FNB) significantly improves postoperative analgesia compared with systemic opioid therapy at least during the first 24 hours after TKR or ACL reconstruction  although some studies show a limited benefit of single-injection FNB as an analgesic technique during TKR or ACL reconstruction.  The pain after TKA is severe and does not fade noticeably for 48–72 h after the surgery. Effective pain control allows for earlier ambulation and initiation of physiotherapy, which hastens recovery, A reduces the length of stay in the hospital, and lowers the risk of postoperative complications, such as thromboembolic disease or nosocomial infections. Bupivacaine is the standard, long-acting local anaesthetic used in regional anaesthetic practice together with ropivacaine, a N-propyl homologue of bupivacaine and a pure S(-) enantiomer . Ropivacaine has shown a reduced potential for central nervous system toxicity and cardiotoxicity in laboratory experiments and in healthy volunteers. Dexamethasone added to local anaesthetics (LAs) appears to prolong single-injection nerve block. The analgesic effects of spinal and systemic corticosteroids combined with LAs have proven to be effective in humans, whereas dexamethasone microspheres have increased block duration .

The purpose of the study is to compare difference in post operative analgesic duration, amount of sedation and systemic side effects in 0.25%bupivacaine and 4mg dexamethasone with 0.25% ropivacaine and adjuvant 4mg dexamethasone using femoral nerve block as a post operative analgesia in TKR