All authors agree it is easier to measure movement at a single joint than at many sites. More pertinent is whether the information obtained in this way reflects properties of joints in other regions of the body. This is clearly not so articular is present. However, provided like joints are compared and the comparison is limited to joints where movement is constrained by ligaments rather than bone, the extrapolation has theoretical attractions. Th correlations obtained between scoring systems in the selected populations quoted earlier in this chapter are all highly significant, suggesting that หน้า22 information from a single joint can indeed be extrapolated. The unanswered question, therefore, is what determinant of joint mobility the three scoring systems were measuring