To date, the administration of local anesthetics through a catheter next to the femoral nerve has been shown to improve pain relief after knee replacement surgery. These pain relief benefits have resulted in faster recovery after total knee replacement. Until recently, catheter techniques were not frequently used due to technical difficulties encountered when attempting to find the femoral nerve, as well as difficulties related to catheter displacement after surgery. Due to recent improvements in nerve and catheter localisation, catheter installation has become easier, more precise and more reliable. However, the distance at which the catheter must be advanced next to the femoral nerve in order to provide the best pain relief remains unknown. Insertion distance could influence the initial quality and distribution of the freezing, its duration, or both. Therefore, this study is designed to compare two catheter insertion distances, in order to help determine which is best for pain relief after knee surgery.