When driving at about 50 mph on a highway, there was a loud noise from the rear of the vehicle (something breaking) and the vehicle immediately veered into the oncoming lane (thankfully there was no traffic coming towards us, it is typically a busy road). While braking, I was able to steer it back towards the right, but soon after lost complete control of the vehicle and could not steer. The traverse went into a ditch and rolled with myself and two young passengers. Two vehicles that were behind us stopped to aid. The driver immediately behind me said there was nothing unusual (no smoke, sparks, etc) until we lost control. He checked the roadway where it happened and found a sheered off bolt. When we got the traverse to the wreckers, they lifted it up and within a minute or two found the location the bolt came from. It was the rear passenger side upper control arm knuckle bolt. I didn't see any recalls on something like this, but I do not believe something like this should have happened in a vehicle that has just 49,510 miles and barely any rust on it. I need answers. My family and friends could have been attending a funeral this week had circumstances been slightly different. I can provide pictures, but the upload link would not work for photos even after converting to proper size and file type. I have the collision report number but not the actual report on hand just yet.