Best way to build up hocks on my 17yr old mare. Yes she gets injected but what workouts can I do to help her feel her best. Anyone else run older mares and succeed? 

Not necessarily "build up" hocks because its wear and tear on them. So save them. Don't be doing a ton of circles and don't run/work the pattern if it isn't nececssary. Save the joint by not overusing it and start on adequan.

Don't over do it. Keep them limber, long walks less *hard* work, but be consistent. Don't let them get out of shape. 

Adequan, previcox things like that will help.