The tibial tuberosity index assesses the relative thickness of the tuberosity on radiographs. The line through the base of the tibial tuberosity is parallel to the midvertical tibial line. The midvertical tibial line is determined by measuring the middle of the projection of the tibia from four points located at various vertical levels of the cortex of the proximal part of the tibial cortex. The height of the tuberosity is measured from the line running parallel to the midvertical tibial line and passing through the base of the tuberosity. The base of the tubercle is determined by adjusting the line through the estimated base of the tibial tuberosity so that it is parallel to the midvertical tibial line and delineates the tibial tuberosity from the anterior tibial cortex. The tibial tuberosity index is the ratio of the distance from the top of the tuberosity (dotted line farthest to the right) to the parallel line of the anterior tibial cortex (middle dotted line B) to the distance from the top of the tibial tuberosity to the tibial midline (dotted line farthest to the left A + B). The tibial tuberosity index is calculated by dividing the length of the horizontal line B by the sum of the horizontal lines A and B.