The rowing ace was filming a cycling programme for the Discovery Channel in the U.S. when he was hit by a truck in Arizona.
He has revealed the accident jolted his brain and he now suffers problems with concentration, memory and his temper - but Cracknell's recuperation was boosted with some good news when his wife Beverley Turner discovered she is pregnant.
The gold medal-winning sportsman tells Britain's Daily Telegraph, "When the truck's wing mirror hit me on the back of the head some of the impact was absorbed by my helmet... Although I was very disorientated and agitated for some time, just knowing I'd been hit by a truck made me feel lucky to be alive...
"There is a crucial window of three weeks from the accident to regaining consistent memory. Within that window a full recovery is on the cards; outside of that and there are no guarantees. I have 'islands of memory' but no consistency, so there are no guarantees. I can't drive and will have to be reassessed.
"I can't drink for between six months and a year as the neurons in my brain rejoin. I will never be able to work at the same pace as before or be able to grasp complex theories. Although to be honest I've always tended to steer clear of the latter."
But Cracknell is adamant he will make a full recovery to be at his wife's side when she gives birth.
He adds, "I'm so proud of her and our unborn child for the way they have looked after each other and I'm determined to make sure I make a full recovery to be there for (my family)."