Mylène Jansen

KIDA performance in severe OA 217 11 Figure 1 : Example of KIDA analysis. The height of the medial and lateral tibial eminence is determined by placing 2 circles on the top of the eminences; the program calculates the distance in mm from the bottom of these circles to the line at the proximal tibia (Figure 1). Next, the user positions 4 circles, 1 at each corner of the joint, following the original bone lines (Figure 1). The user then indicates the outer osteophyte borders; only the borders within a quadrant (blue/green lines in Figure 1) are included. The program then calculates the osteophyte area in mm 2 for each of the 4 areas (yellow in Figure 1). Using the middle 8 small circles at the bone-cartilage interface, a new line is generated for both the bone edges of the femur and the tibia separately (not displayed in Figure 1); these 2 lines are used to calculate the joint angle in degrees. A negative angle indicates medial joint space narrowing. Lastly, the program gives a vertical line at the narrowest point between these 2 lines, within the joint edges, suggesting the location of the minimum JSW. Since the bone edges are not fully straight, the user can manually adjust the lines to indicate the actual minimum JSW (this does not affect the joint angle). The program then calculates the distance between the 2 horizontal lines at the location of the vertical line as a measure of minimum JSW in mm. Additional details of the analysis process can be found in the original publication. 5