Unknown. During a basic collision Avoidance maneuver performed by myself on the highway at speed of aprox 60MPH the steering suddenly became non-responsive, resulting in my inability to maintain directional control and cause a collision. The vehicle continued traveling before coming to its final resting position. During this sequence, the driver-side front suspension assembly sustained a catastrophic separation before the impact The steering knuckle was no longer attached to the vehicle, the strut was broken, and the driver-side wheel/tire ultimately ended up underneath the vehicle when the vehicle finally come to a stop . During the event The driver-side axle shaft completely detached and somehow come out of the transaxle housing and was found a significant distance back along the roadway, a great distance back before the initial impact . indicating that it separated before the vehicle reached its final resting position. It is in my strongest opinion the maneuver itself could have potentially been cause of the catastrophic event. And is potentially why I could not maintain complete complete control of vehicle the whole time.