I don't have any personal experience in dealing with capped hocks so here's a google article for you, as I don't want to tell you the wrong thing! Capped Hock
As for the bone spurs, a bone spur is a formation of extra bone that the joint starts to grow, where there is some damage to the joint. In the case of my own horse, he was losing some joint fluid from a joint in his hock (onset of arthritis) and this causes the bone ends to come together and start to rub, causing irregular bone growth.
There are other causes, but this is most common.
Often you won't notice anything different about the horse, and then one day they'll be lame and swollen, totally out of the blue. And it's extremely common for them to have it flare up as they're being brought back into work after a spell.
Some bone spurs don't cause any problems and go totally un noticed, others will give the horse grief to no end.
There's a few different methods of treatment, the vet can surgically remove the spur using keyhole surgery, they can use shockwave therapy (an instrument that sends shock waves into the joint and essentially breaks up the spur from outside the leg), they can chemically inject into the joint under surgical conditions, to encourage fusion of the joint which will leave the horse out of pain and in most cases, able to return to full work without any soundness problems.
In the end, it depends on which joint is involved (the hock is made up of multiple small joints) as to what treatment can be administered. I got very unlucky with my horse, who developed the spur on one of the smallest joints in the hock, meaning they cannot surgically remove it or perform shockwave on it, as the risk of damaging the joint itself even further is too great.
So now I am stuck playing a waiting game, sitting back with my fingers crossed that the joint will fuse naturally and I'll be able to get my boy back into work in 6 months.
I hope for your sake that this won't be the case with your horse.