Hello Wendy,
I do not know of any research using such devices/treatment on horses. I cannot see why they would not work as they would in people but how effective are they? Also skin sensitivity may be a problem.
Finding the right treatment will depend on two things: one, what is the cause of the swelling and lameness and two, what is the goal for treating this horse. First I would recommend you switch from bute powders to firocoxib (https://horseadvice.com/horse-equine/medications/anti-inflammatories-nsaids-steroids-arthritis-rx/equioxx-firocoxib/) for a safer oral NSAID. Talk to your veterinarian for confirmation and possible inexpensive alternatives to the horse product. For an overview of the causes of swelling and lameness of the fetlock see https://horseadvice.com/horse-equine/diseases/lameness-in-horses/diseases-of-the-lower-limb/overview-of-fetlock-ankle-lameness/.
DrO