The Effect of Axial Load in the Tibia on the Response of the 90° Flexed Knee to Blunt Impacts with a Deformable Interface
Lower extremity injuries are a frequent outcome of automotive accidents. While the lower extremity injury criterion is based on fracture of bone, most injuries are of less severity. Recent studies suggest microscopic, occult fractures that have been shown to be precursors of gross bone fractures, may occur in the kneecap (patella) for impacts with rigid and deformable interfaces due to excessive levels of patello-femoral contact pressure. One method of reducing this contact pressure for a 90° flexed knee is to provide a parallel pathway for knee impact loads into the tibial tuberosity. Yet, blunt loads onto the tibial tuberosity can cause posterior drawer motion of the tibia, leading to injury or rupture of the posterior cruciate ligament (PCL). Recently studies have shown that axial loads in the tibia, which are measured during blunt loading on the knee in typical automobile crashes, can induce anterior drawer motion of the tibia and possibly help unload the PCL.