For the ACB: ultrasound survey at the medial part of the thigh will take place, halfway between the superior anterior iliac spine and the patella. In a short axis view, the femoral artery will be identified underneath the sartorius muscle, with the vein just inferior and the saphenous nerve just lateral to the artery. The needle will be introduced in-plane and 2 to 3 mL of LA bolus (0.2% ropivicaine) will be used to verify correct placement of the needle in the vicinity of the saphenous nerve in the adductor canal. A bolus of total volume of 20 ml of Ropivicaine 0.5% will be injected through the needle. The catheter will then be introduced and advanced 2-3 cm beyond the tip of the needle.