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Ratzlaff, Charles, Erin L. Ashbeck, Ali Guermazi, Frank W. Roemer, Jeffrey Duryea, et C. Kent Kwoh. "A Quantitative Metric for Knee Osteoarthritis: Reference Values of Joint Space Loss." Osteoarthritis Cartilage 2018.

Ratzlaff, Charles, et al. "A Quantitative Metric for Knee Osteoarthritis: Reference Values of Joint Space Loss." Osteoarthritis Cartilage 2018.