Additional Study Information: The Bone Bioengineering Laboratory and Division of Rheumatology at CUIMC are doing a study to learn more about the progression of knee osteoarthritis (OA). We are recruiting patients 55-75 years old who may or may not have OA of the knee(s). This study involves a screening and enrollment visit with annual visits for 3 years. Study activities include a hip and knee assessment, questionnaires, two small blood draws, yearly x-rays of both knees, and yearly CT and MRI scans of one knee. With these tests, we hope to understand how and why OA occurs and why some people with OA progress faster than others.