Total knee replacement is often associated with severe postoperative pain, especially in the first 24 hours. Patient controlled analgesia (PCA) and continuous femoral block with PCA are commonly used to treat postoperative pain after total knee arthroplasty. However, PCAs use opioids. Opioids are excellent painkillers but their use is hampered by side effects such as nausea, vomiting, bowel dysfunction, urinary retention, pruritus, sedation and respiratory depression. We propose to test the hypothesis that adding a low dose lidocaine infusion to PCAs will lower the amount of opioids that these patients receive, thereby improving patient safety while still providing adequate analgesia. In addition, continuous femoral block has been shown to provide superior postoperative pain control when compared to morphine PCA. Therefore, postoperative pain levels of study subjects will be compared to those subjects who receive a combination of a continuous femoral block catheter with a PCA.