The anaesthetic management of patients undergoing total knee replacement is still not standardised. Epidural analgesia is common, but is associated with bilateral lower limb motor block and limited mobilisation. Spinal anaesthesia with intrathecal morphine provides good pain relief, but only for 12 to 16 hours, and is often associated with nausea and vomiting. Combined single injection femoral / sciatic blocks give good pain relief, but for a variable length of time (between 12 and 24 hours).