Ankylosing spondylitis (AS) and rheumatoid arthritis (RA) are progressive chronic rheumatic diseases. Coexisting AS and RA is a rare condition. In these diseases, the possibility of a difficult airway and failed neuraxial block is increased. A 65-year-old female patient coexisting AS and RA, which is scheduled for regional anesthesia for total knee arthroplasty. After neuraxial block was failed, the patient was successfully applied a combined sciatic-femoral nerve block. As a result, in coexisting AS and RA, peripheral nerve blocks can be applied an alternative anesthetic method to general anesthesia and neuraxial block for lower extremity surgery.