Inclusion Criteria:  - patients undergoing painful foot and/or ankle surgery with a planned popliteal sciatic perineural catheter for postoperative analgesia  Exclusion Criteria:  daily opioid use within the previous 4 weeks clinical neuromuscular deficit of either the sciatic nerve and its branches and/or innervating muscles morbid obesity [body mass index > 35 kg/m2] surgery outside of the ipsilateral sciatic and saphenous nerve distributions [e.g., iliac crest bone graft] pregnancy incarceration