Background: Ambulatory knee procedures have become increasingly common due to the effectiveness of the anesthetic techniques that facilitate rapid and safe discharge. Objective: To compare between spinal anesthesia versus ultrasound guided combined fascia iliaca compartment and sciatic nerve block for knee arthroplasty. Patients and Methods: This study enrolled 40 patients (ASA) physical status (1, 2, 3), 20 patients in each group scheduled to undergo elective unilateral knee arthroplasty procedures. All patients of block group (group B) received premedication with 0.05 mg/kg midazolam intravenous injection. Group (S) (20) patients received spinal anesthesia attained by 20 mg/4ml of 0.5% heavy bupivacaine together with fentanyl 25 µg injected aseptically using a 22-G needle in subarachnoid space at the L4-5 level then the patients were required to wait in the lateral decubitus position on operated side for 5 minutes. Group (B) (20) patients received ultrasound guided combined fascia iliaca compartment and sciatic nerve block using a 22-G needle. Results: In the present study, sufficient block could not be obtained in two patients in block group, they shifted to general anesthesia and excluded from the evaluation, and we replaced them by two other patients. Conclusion: The preferential selection and successful use of anesthesia techniques are based on not only having a short preparation time and rapid onset of action, but also on providing lower rate of complications and adverse events, a longer duration of analgesia, good patient satisfaction and optimal condition for patient discharge compared with other available agents.