This study aims to evaluate the efficacy of dexmedetomidine in reducing the incidence of postoperative delirium and cognitive dysfunction in elderly patients undergoing total knee arthroplasty (TKA). The study will compare the outcomes of patients receiving dexmedetomidine to those receiving a standard anesthetic or sedative, focusing on factors such as patient characteristics, surgical duration, and postoperative care. The research will explore the potential neuroprotective effects of dexmedetomidine and its ability to mitigate the risks associated with anesthesia and surgery in vulnerable elderly populations.

Inclusion Criteria:

• Patients with Severe chronic knee osteoarthritis inducing limitation of movement and required knee replacements;
• Patients of American Society of Anesthesiologists Classification grades II-III;
• Patients free of exclusion criteria.

Exclusion Criteria:

• Patients of American Society of Anesthesiologists Classification grade >III;
• Patients show a high risk for getting Post Operative Delirium or have severe cognitive dysfunction;
• Patients had a history of uncompensated cardiac, renal, or hepatic diseases;
• Patients had uncontrolled diabetes mellitus or hypertension;
• Patients had other causes for limited movement;
• Patients had autoimmune disease, coagulopathy, severe anemia with a hemoglobin concentration of <7 g%;
• Patients had local bone disorders that may prevent prosthesis stability;
• Patients had allergies or contraindications to the study drugs.