Best maintenance of osteoarthritis in a long distance horse?

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Kristi iluvdez@yahoo.com
My 10 yoa Arab has been diagnosed with arthritis in his right hock.
The vet said that it's mild at this stage (barely Grade .5 after
flex test) and that x-rays wouldn't show any unusual changes
yet (signs I've noticed are "dropping out" behind at the trot, 
and the inability to handle being trailered backwards in a slantload
like he used to prefer - he "locks up" and can't move his hind leg
for a few moments while unloading after a long trailer ride).
The vet recommended continuing J-Flex orally and to start a series
of 5 Adequan injections in the spring. My goal is to do as much
prevention as possible without overkill on the supplements. 
For those of you with arthritic horses, what have you found that
works to slow down the degenerative process best? I realize that
horses react differently to different treatments, but I'm curious
what long distance horses seem to do best with - Adequan? 
Cosequin? Chondroit/glucosamine? Etc? My horse has 1,000 NATRC 
miles and several LD's under his belt, and my goal is (was?) to
do 50's with him. Thanks in advance for advice. Kristi