Support Glucosamine

horse supplements for a young barrel racer?
i have a 6 year old game horse who LOVES to run and show(just started gaming this spring) yet, he has a twisted front leg. he has had it is whole life and has never been lame or had ANY issues. it is getting better with ferrier help, but i am afraid of it becoming arthritic in the future. so i ask these questions:
1. would it be a good idea to put him on supplements this early in age? or should i wait a little longer? if so, which age should i start?
2.do you know of any supplements that would help prevent joint issues that are less than 15$ a month?
3. which of these 2 would be better for him:
http://www.horse.com/Horse-Supplements/Joint-Support/B-L-Pellets-BWB16.html
http://www.horse.com/Horse-Supplements/Joint-Support/Glucosamine-Joint-Liquid-BWA81.html
thanks!! 
please answer these questions as if you were talking about your own horse. like, as if he were your own horse, what would you do?
1. You could start supplementing him early, but 6 might be a bit too early. I'd say starting him on a glucosamine and chondroitin sulfate supplement around 10 would probably be prudent, but at 6 it's more likely a waste of money.
2. Chondroitin sulfate and glucosamine have the best track records for arthritis prevention and treatment. There are a bunch of cheap versions, but many question their effectiveness. Some have reduced dosages that may not be therapeutic, some may not be in a form that is accessible to the body for use. The best versions (cosequin is one I've liked) tend to run about a dollar a day, but are worth every penny.
3. At this point I wouldn't recommend either of those products. The one is glucosamine, which would be helpful for an older horse, but probably not a six year old, and I'd prefer a version with chondroitin sulfate as well. The BL is a great herbal bute alternative for a horse with active pain, but you said the horse isn't lame, so file it for possible future reference, but don't waste your money.
For right now, I'd put him on antioxidants (Vitamin E, Vitamin C, Selenium, Vitamin A) these protect his body from natural but damaging free radicals, they essentially help to slow down the effects of aging. Vitamin A usually isn't supplemented as it is easier to overdose, and can have some really nasty implications if you do overdose it. There are a bunch of E, C and selenium supplements on the market though.
I like this one:
http://www.smartpakequine.co/ProductClass.aspx?productclassid=131
it is harder to find, but it has lots of E,C, and selenium as well as other vitamins/minerals and yeast cultures which are good for the stability and efficiency of his digestive tract. A multi vitamin and mineral supplement with high levels of antioxidants is something I'd recomend for any competition horse at any age, they are safe, affordable, and can do wonders for the horse's long term health.
Edit: Link may not work. (Agh!) Product name is: Vita-Key Equine Supplements Antioxidant Concentrate.