• Garry E Gold, Thor F Besier, Christine E Draper, Deanna S Asakawa, Scott L Delp, and Gary S Beaupre.
• Department of Radiology, Stanford University Medical Center, California, USA. gold@stanford.edu
• J Magn Reson Imaging. 2004 Sep 1; 20 (3): 526-30.

PurposeTo measure contact area of cartilage in the patellofemoral joint during weight bearing using an open MRI scanner.Materials And MethodsWe developed an MR-compatible back support that allows three-dimensional imaging of the patellofemoral cartilage under physiologic weight-bearing conditions with negligible motion artifact in an open MRI scanner. To measure contact areas, we trained observers using a phantom of known area and tested intra- and interobserver variability. We measured in vivo contact areas between the patella and femoral cartilage with the knee in 30 degrees of flexion, loaded and unloaded, in six volunteers.ResultsWe were able to measure the contact area of the patellofemoral cartilage with small interobserver (CV 7.0%) and intraobserver (CV 3.0%) variation. At 30 degrees of knee flexion, mean contact area increased from 400 mm2 (unloaded) to 522 mm2(loaded to 0.45 times body weight per leg).ConclusionUsing an open magnet and specially designed apparatus, it is possible to image the patellar cartilage during physiologic loading. Knowledge of patellar cartilage contact area is needed to assess patellofemoral stress, which may be increased in patients with patellofemoral pain syndrome.Copyright 2004 Wiley-Liss, Inc.

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