A flexion test is a preliminary veterinary procedure performed on a horse, generally during a prepurchase or a lameness exam.
An increase in lameness following a flexion test suggests that those joints or surrounding soft tissue structures may be a source of pain for the horse.
This flexion is usually performed by pulling the toe of the hoof backward towards the cannon bone, and holding sustained pressure on the joints.
Flexion may be performed by lifting the forelimb (antebrachium) so that it is parallel to the ground, while allowing the knee and distal limb to hang free to help prevent pressure on these joints.
A second method, involving placing the hoof on a wedge so the toe is lifted up relative to the heel, subsequently increases deep digital flexor tendon tension and pressure on the navicular bone.
[5] The flexion test is less useful to evaluate for subclinical joint disease, since a significant number of sound, unaffected horses can produce slightly positive results.
[6] Additionally, forelimb flexion tests have been shown to have poor predictive value for future soundness or unsoundness, and are best interpreted in cases of clinical lameness, joint effusion, reduced range of motion, or pain on palpation.
[2] Unfortunately, a positive response to forelimb flexion tests is one reason horses may be deemed unsuitable for purchase during the prepurchase exam.
While there have been many purchase exams discontinued solely because a positive response to a flexion test in one or both forelimbs, there's really nothing in the veterinary literature to support such an action.