This is a three-group randomized placebo-controlled double blind trial to assess which postoperative analgesia is best after total hip replacement. The conventional analgesia includes both intrathecal morphine at surgery and Patient Controlled Analgesia (PCA) with morphine in the first 48 hours after surgery. This will be compared with two experimental groups which will receive either intrathecal morphine and PCA with placebo or intrathecal placebo and PCA with morphine. Escape medication with intramuscular morphine is available in all groups. A total of 120 patients will be randomized.