Weidow, J., Cederlund, C.-G., Ranstam, J., & Kärrholm, J. (2006). Ahlbäck grading of osteoarthritis of the knee: Poor reproducibility and validity based on visual inspection of the joint. Acta Orthopaedica, 77(2), 262–266. https://doi.org/10.1080/17453670610046000