I have been knocked out two times.
1. I was replacing the steering wheel on my Ford 800 and the wheel was corroded to the steering shaft. I used a gear puller and a long handle cresent wrench. When the wheel came loose it hit me under the chin and when I awakened I was lying next to the outside rear wheel. my mouth was bloodied and I first thought my jaw was broken however I had just biten the end of my tongue.
2. I was unloading a lawn tractor from my pickup. I ignored every safety rule that my dad tought me. I was using alumimun ramps not anchored, unloading on concrete and was sitting on tractor. I guess the deck hit one of the ramps and the tractor went one way and I went the other. I landed on my bottom and it threw me backward hitting my head on the concrete. our neighbor who is a nurse saw it happen and applied ice to my head. It was touch and go for a few hours with brain swelling. The accident happened at approx. 6:30 p.m. however I don't remember anything from noon that day until 3 days later. It was several months before I regained short term memory.
As a foot note: a couple of months I had a call from a law firm and was told they could get me money from the ramp company. I told them why would I sue someone for my carelessness.