Knee motion analysis of the non-loaded and loaded knee: a re-look at rolling and sliding.

Many studies of knee motion have been reported in the literature over more than 100 years. Of particular interest to the analysis presented here is the work of the Freeman group, who elegantly measured tibio-femoral kinematics in studies made on cadavers and the knees of living individuals using MRI, anatomical dissection and RSA. We examined and re-evaluated the data collected by Freeman's group and suggest that their conclusion should be considered to be incorrect, since their methods of evaluation were oversimplified from the mathematical and physical perspectives. By applying appropriate methods, however, it is possible to show that the same data yield important insights into physiological knee kinematics and reveal that the rolling-sliding relationship depends on the degree of flexion and on joint load in the medial and lateral compartment, as well. In the initial range of flexion, a considerable amount of rolling was found to occur. Based on this analysis, it is possible to gain useful insights of value for the design of total knee replacements.