This is a randomized study which will compare three femoral nerve catheter insertion techniques. Subjects will be randomized into one of thee groups, Group 1: ultrasound guided femoral nerve catheter using a stimulation needle and stimulating catheter, .Group 2: ultrasound guided femoral nerve catheter using a stimulation needle, but non-stimulating catheter, or Group 3: ultrasound guided femoral nerve block without stimulation.