Knee osteoarthritis (OA) is the most common clinical presentation of osteoarthritis, and has been estimated to affect 12–16% of the population older than 60 years in the US [1]. A biomechanical risk factor that has been linked to knee OA is the changes in the local loading and the contact area between the cartilage surfaces [2]. Investigation of such factors requires precise measurement tools to determine knee joint positioning and contact areas. Clinically, MR images of the knee are most frequently acquired in the supine position; such images are not representative of the loading conditions experienced functionally in the weight bearing knee joint. With the advent of vertically open MRI (e.g. Upright MRI, Fonar Corporation, Melville, NY), it is now possible to scan the knee in fully upright weight bearing conditions representing truly functional positions. To measure sensitive variables such as joint positioning and cartilage contact, it is important to minimize subject movement in order to obtain high quality images. In MRI, increased scan times allow for data of improved signal to noise ratio and resolution; however, long scanning durations without subject movement are not feasible, particularly in individuals with symptomatic knee OA.

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