The pre-purchase examination is the single most important protection you have, and the professionals who buy horses for a living never skip it. It is a veterinary examination, arranged and paid for by you, that tells you the condition of the horse before you commit. Its job is not to pass or fail the horse, because almost no working horse is perfect on a thorough exam. Its job is to tell you what you are taking on, so that you can decide with open eyes.
One rule about the vet is not negotiable: the vet works for you and must be independent of the seller. Not the yard’s regular vet, however convenient, and not “our vet can do it while you’re here.” The seller’s vet has a conflict and may hold history they are not free to share. If a seller ever discourages you from getting your own independent examination, or pushes you toward their vet, treat that as the clearest warning sign in the entire process and walk away. Honest sellers welcome a proper vetting, because it protects them too.
A standard European examination looks at the horse at rest and in movement, includes flexion tests and work on the lunge and under saddle, and at the sort of prices dressage horses command it usually adds a set of X-rays and a blood sample held in storage. For a buyer who cannot be there, arrange for all of the images and the report to be sent to your own vet at home for a second opinion before you commit, because reading X-rays is a matter of judgement and two readings are better than one. The stored blood is a quiet but important safeguard: if the horse turns out to have been sedated or medicated for the viewing, that sample can be tested later, and knowing it exists keeps everyone honest.
When the results come back, most horses will show something, and that is normal. The question is never whether the horse is flawless. It is whether the findings are compatible with the work you want to do, at a price that reflects them, with an understanding of what your insurer will and won’t cover. Your vet answers the first part. You answer the rest.