Post-operative pain following total knee replacement can be disabling and sometimes lead to
the need for prolonged hospital stay. Therefore development of improved post-operative
modalities for total knee replacement surgery pain control is important. High-resolution
ultrasound (US) allows accurate visualization of nerves and surrounding structures and can
lead to higher success rates of nerve block. The investigators aim at comparing the analgesic
efficacy of ultrasound-guided nerve block catheter compared with epidural analgesia for
patients with knee OA who underwent unilateral total knee replacement.