Veterans have much higher risk of osteoarthritis (OA) then the general population. Knee OA is common among Veterans and is a leading cause of disability. The earliest stages of OA development, where the joint cartilage wears away, is usually painless. By the time Veterans experience symptoms, the OA is typically advanced and there is nothing that can be done except palliation until the joint is replaced with metal and plastic. If there was a blood test to provide early warning of cartilage wear and joint deterioration, Veterans could potentially be treated early enough to slow down or even prevent OA. So far, development of such a blood test has proved elusive. The investigators propose a new method to amplify the signs of cartilage wear in the blood by challenging the affected joint with a walking task. Similar to a cardiac stress test, this walking challenge may help to separate joints at risk from healthy joints. The investigators will also see if this 'OA stress test' can show if a simple and inexpensive load-modifying shoe can improve joint health in Veterans with early knee OA.