Rear-end collisions are usually unexpected, happening when you're slowing to a stop or even when you're parked. Another driver may not see that you're ahead of them, or they might fall asleep behind the wheel and hit your vehicle. In some cases, the drivers are texting and don't look up in time to stop.
In any rear-end crash, one of the greatest risks to you is the potential whiplash you could suffer. Whiplash is serious because it can badly damage your tendons and ligaments in your neck. There is swelling and a loss of function in some cases. Headaches are common with this injury, too.
Another serious injury that could take place is a head injury. When you're hit, your head may whip forward. You could suffer injuries from hitting the air bag, or if it doesn't deploy, injuries from hitting the wheel or window.
While rear-end crashes do tend to happen with less force (one person is usually stopped or slowed, with the other traveling at full speed), the chances of developing an injury are still high. People in the rear of the vehicle could be pinned or injured from a direct hit. If there's a vehicle in front of you, your car could be pushed into it, causing further damage and crushing injuries.
If you're hurt in a crash like this, it's essential that you go to the hospital. There are so many kinds of injuries that you could suffer that you need to have a full exam. The driver responsible for the crash may be held liable for your medical expenses.