his study is being done because total knee replacements can leave patients with considerable pain after surgery. Therefore, many studies have been done to find the best ways to control knee pain after the surgery. Currently, a popular approach is to use many different techniques to control the pain. This includes injecting freezing (local anesthetic) into the spinal column (spinal anesthetic), injecting freezing close to the nerves of the knee and using various kinds of medications (e.g. narcotics and anti-inflammatory medications). Studies have shown using this a combination of techniques can reduce pain and allow earlier discharge from the hospital. However, one downside to this approach is it does not usually control the pain in the back of the knee. One new technique has been used to try and overcome this. This technique is called a "posterior cruciate ligament block" or "PCL block". It involves injecting a drug into the back of the knee which will block the nerves in this area. Sometimes the investigators refer to this as "freezing".