My horse is getting os phos for his hocks next week.  Just wondering if anyone had great results with it

We tried it on one that had a little navicular and fusing hocks at the same time.  I think it slowed the fusing process for the hocks.  

Depends on age of the horse and what's going on.  I wouldn't use first if you haven't tried a good dose of cortisone and HA. 

Oh we have tried everything this has been going on for 2 years and I've spent close to 5grand on him

I used it years ago for a navicular type issue and an added bonus was how it affected her hocks.

What stage are the hocks in?

It can be a great drug but its a slow burn.. usually takes a good 60 days to notice results. So I wouldn't expect anything immediate, and wouldn't make any judgment calls prior to 60 days.