If there is tendon and ligament issues, included with the joint issues - I would look at SmartPaks suppliments.
1st, I LOVE Smartpak Equine - they are fabulous to deal with, fabulous to do buisiness with and are quick to answer any questions you have educatedly.
I currently get through Smartpak Equine 4 suppliments, which they conveniently package up in the doses my horse needs *weight wise* for his daily feedings. I love how convenient everything is!
There are a few boarders at my barn who have the same issues with their horses as you do - Joint, Tendon and Ligamnet...and they swear by this product: SmartFlex Repair Pellets - Horse Joint Supplements from SmartPak Equine
This is one of the 4 suppliments my guy has been on for a month now, because he injured his hock in January. I am quite pleased with the results!
With injections - I would go more towrads Adequan than Legend personally - and yes, it is expensive *the loading doses are*
The cost of Adequan *Which is cheaper than Legend* is $40 a bottle, and for the loading dose, you have to go with 1 bottle *which is one full injection* every 4 days.
So that's 7 bottles in a month for the loading dose - which comes out pretty pricey.
After the loading dose month is done, then you go to 1 bottle a month. It's the loading dose that killed me, my Husband said no way hosay.....
SO instead of Adequan, I went to Glucosamine IM which is $25 a bottle which lasts 12 months.