We will also ask patients to perform 3 functional tests at each of these office visits. These 3 tests will be performed on a raised platform that is approximately 2 inches above the floor. For the first test, the patient will be asked to stand still with knees straight for two seconds, and then be asked to stand still with knees bent to 45 degrees for two seconds. For the second test, the patient will be asked to stand up from a seated position. For the third test, the patient will be asked to step up onto a four-inch wooden box and then step back down onto the platform. Prior to testing, the patient will be allowed to practice each of these tests as many times as necessary until he/she feels comfortable. During testing, an investigator will help make sure that the patient is able to safely and properly perform 3 repetitions of each test. We will not ask patients to perform one or more of the functional tests if they are unable to perform the test without constant use of their arms for support.