Flexion Test - Specificity

Specificity

Flexion tests are rather nonspecific, as each test flexes multiple joints (such as the stifle and the hock, or the pastern and the navicular area). So while they can help localize a lameness issue to one particular leg, or even to a few joints in the leg, they can not pinpoint it. In lameness exams, the next step is usually to perform nerve blocks to help localize, confirm, or rule out a suspected source of lameness. A local anesthetic is injected in a specific joint and sensation is temporarily inhibited. Once the area is sufficiently numbed, another flexion test is performed. If the horse is no longer lame, the joint or area where the block was performed is the likely site of the problem. If the horse is still lame, another site may be blocked and more flexion tests performed.

False positives may occur, however, especially if excessive force was placed on the joint, and many horses can continue to perform their jobs quite well despite having "failed" a flexion test. It is therefore important for owners to continue to perform diagnostics if they suspect there is a problem. Additionally, a veterinarian may flex both fore or hindlimbs separately for comparison, to determine which limb is experiencing an unknown lameness, or if the few uneven steps are "normal" for the horse.