[The tension band effect of the iliotibial tract]

There is an unreconciled discrepancy between the course of the iliotibial tract described in most anatomical textbooks and the results of photoelastic experiments performed by Pauwels (1948), in which he demonstrated the principle of the tension band effect that decreases the bending stress of the femur. If the photoelastic experiments are performed according to the anatomical description of the attachments of the iliotibial tract between iliac bone and tibial condyle not only is the tension band effect lacking; the stress is even increased. Our reinvestigation of the course of the iliotibial tract shows that the iliotibial tract is not fixed at the greater trochanter, as Pauwels assumed in his photoelastic experiments. Rather, the tendon of the gluteus maximus and a major portion of the iliotibial tract intermingle near the gluteal tuberosity. As a result, the iliotibial tract is also attached to the proximal end of the femur. If a model is constructed on the basis of this finding, the simulation of traction between gluteal tuberosity and the tibial condyle results in a decrease in the bending stress on the femoral shaft. Thus, the results of the present morphological and functional investigations confirm the biomechanical tension band effect of the iliotibial tract on the femur via the attachment to the femur mediated by the tendon of the gluteus maximus.