Evaluation of the response of mechanical pedestrian knee joint impactors in bending and shear loading.

The knee joint is especially susceptible to injury in the pedestrian impact loading environment. However, the mechanical response, injury mechanisms and injury thresholds for lateral impact loading of the knee joint remain poorly understood. This paper reviews real world crash data and PMHS tests and identifies knee joint injuries commonly seen in pedestrian crashes. This is compared with results from knee joint shearing and bending tests reported in the biomechanics literature. It is shown that lateral knee joint shearing is unlikely to occur in real world pedestrian crashes. Next, the ability of mechanical knee joint impactors, commonly used in vehicle countermeasure development, to replicate PMHS tests is studied by performing quasi-static and dynamic lateral bending and shearing tests on the TRL legform and the POLAR II knee joint. The test boundary conditions chosen are similar to those used in PMHS knee joint tests performed at the University of Virginia. Results show that both mechanical impactors are stiffer than PMHS knees in bending, although the relative difference is smaller with the POLAR II knee. In shear loading, the PMHS knee is capable of much higher shear displacement than that permitted by the TRL impactor. While the POLAR II knee permits larger shear displacement, the loads required to produce these displacements are much higher. For the covering abstract see ITRD E825082.