Shameless plug - but I have had huge success with laser therapy!! Skip the "Quantum Laser" junk and go for either a rental of a Centurion machine or go full out for some Pegasus treatments. Centurion will take about a month to start really seeing benefit, but having a trained Pegasus technician come out and laser your horse will show huge results in only a few treatments.
I was sold on massage when I first started having an RMT work on my horses, but laser does such a great job of repairing and relaxing tissue that it is my go to!! The RMT is just icing now.
Were it me I would have the horse on rest for a month, if not two, and be using laser therapy. I would check the horse after a few weeks of therapy.
They say money doesn't buy happiness -- well happiness doesn't buy horses!