Inclusion Criteria:  the ages of 40 and 70 years height 155-170 cm American Society of Anesthesiologists grade I or II . patients underwent total knee arthroplasty under spinal anesthesia  Exclusion Criteria:  patients known to be allergic to any medicines. patients had a history of drug or alcohol abuse. patients were taking opioids or sedative medications, patients Inability to communicate with investigators to evaluate the postoperative pain patients were in need for postoperative ICU hospitalization . patients had a history of psychiatric conditions. Patients with a history of taking pregabalin or gabapentin .