We have used the bio-flow ones and found them to be very effective for a mare with athritic knees. She was retired, but struggling to be field sound. With the boots she trotted in for tea . We have also lent them to friends who have had varying degrees of success.
I have equilibrium magnetic chaps. They keep her legs warm in winter and are machine washable. I only paid £40 for them in the local tackshop. You can't put the magnets directly over the hocks obviously but apparently that doesn't matter as by boosting the circulation to the lower leg you are boosting the circulation to the hock by default, if you see what I mean.
I have some premiere equine magnetic boots.
Definately work, easy to use and in the winter you can take the magnetic lining out and put a normal lining in so they are just like stable chaps
I am following this post with interest as just bought some equilibrium ones for my boy for back legs but also interested in the premier equine ones as heard good reviews about these. The veredus ones are supposed be good but very expensive.