Osteoarthritis (OA) is a chronic degenerative joint disease affecting a large percentage of older people. Post-traumatic CA has been demonstrated to occur following a ligament injury or a single blunt impact to a diarthrodial joint. Lower extremity injuries are a frequent outcome from automotive accidents. The automotive knee injury criterion is based on data for bone fracture in cadaver experiments. The current study combines human cadaver data and a chronic post-traumatic animal model to investigate blunt impacts on the patello-femoral (PF) and tibio-femoral (TF) joints. In Chapter 2, the role of the impact direction on PF joint response was investigated. Many automotive occupants sit with their legs slightly abducted and this orientation can significantly reduce fracture tolerance and change the orientation of patella fractures. Chapter 3 documents that compressive load axially in the tibia on an unconstrained knee will cause the tibia to displace anteriorly with respect to the femur and produce ACL rupture. These data may demonstrate one mechanism for non-contact ACL injuries to occur. Chapter 4 investigates this effect further by documenting the effect an axial tibia load has on the stiffness response of the knee to an anterior knee impact. This combined loading scenario reduces the amount of shear displacement between the tibia and femur. Finally, Chapter 5 documents accelerated subchondral bone changes in rabbits at 12 weeks, following a single blunt impact of approximately 50% of the fracture force. The data presented in this thesis may be applicable to injury prediction and the development of a new knee for the anthropomorphic dummy used in automotive crashes.