Id estimate 3.5yrs, probably unable to breed anyway, thats an old injury, but probably this years.
It looks like the leg was busted and that the bone healed into a big callous knot.
I dont know about that opposite rack to injury theory.
But I would imagine he favors his good side, thus he is banging the developing horns into more brush and stuff as they formed this time around.
Hes obviously not agile enough anymore to duck brush, limbs, fences, etc.
So his good side is taking a beating at every step as they grew.
Of course i could also picture a car striking him in the right rear and knocking his developing rack on the pavement on the left as a more likely cause,
it takes quite a bit i would imagine, to push that main beam back all the way at the base.
Hes obviously still feeding and fat. Right at shooting age anyway.
If the opportunity presents take him.