Patients will receive spinal anaesthesia with intrathecal bupivacaine (17.5 or 15 mg) without morphine, and will receive peri- and intraarticular surgical site infiltration before wound closure with a solution of levobupivacaine 0.5% 2mg/kg body weight (maximum 200mg levobupivacaine) plus 0.5mg epinephrine made up to 100ml with saline. An intra-articular catheter will be placed by the surgeon before closure under the sterile surgical conditions and this will be left in situ in the wound. The patient will receive one further injection of 15ml of levobupivacaine 0.5% at 8am the following morning.

Patients will receive spinal anaesthesia with intrathecal bupivacaine 0.5% (17.5 mg if greater than 70 kg and 15 mg if less than 70 kg) and preservative-free morphine (0.3 mg).

Patients will receive peri- and intraarticular surgical site infiltration to the knee during surgery and before wound closure with a solution of levobupivacaine 0.5% 2mg/kg body weight (maximum 200mg levobupivacaine will be used if the patient's weight exceeds 100kg) plus 0.5mg epinephrine made up to 100ml with saline. An intra-articular catheter will be placed by the surgeon before closure under the sterile surgical conditions and this will be left in situ in the wound. The patient will receive one further injection of 15ml of levobupivacaine 0.5% solution at 8am on the morning of the first postoperative day after which the catheter will be removed.