Diagnosing Lower Limb Lameness in Sport Horses

Diagnostic techniques for lower limb lameness include hoof tester exams, diagnostic nerve blocks (which the veterinarian is about to administer here), and imaging modalities.

Photo: Stephanie L. Church, Editor-in-Chief

“The lower limb is the most common site of lameness in 'English' sport horses,” noted Rick Mitchell, DVM, MRCVS, of Fairfield Equine, in Newtown, Conn. Thus, sport horse practitioners must be well-versed in how to diagnose injuries in this region, he said, and should take a "more aggressive" approach to diagnosing these horses to try to reduce as much loss of training and competition time as possible.

Mitchell, who treats high-performance sport horses in his practice, described his diagnostic approach at the 2013 American Association of Equine Practitioners Convention, held Dec. 7-11 in Nashville, Tenn.

Mitchell started out by characterizing the unique anatomical qualities of the equine hoof that enable it to work as a shock absorber—ranging from the corium parietis and the digital cushion to the natural coffin bone movement within the hoof wall and foot balance—but also predispose it to potential injury. Additionally, he listed important factors that can influence lameness development:

  • Conformational predisposition;
  • Repetitive loading;
  • A long toe, low heel, and/or broken-back hoof-pastern axis;
  • The manner and frequency with which the horse is shod--medial to lateral (side-to-side) balance and breakover (the moment the heels lift off the ground, which can be impacted by how the farrier adjusts the toe) might be major contributing factors; and
  • The footing on which a horse works.

Mitchell noted that the timing of a lameness exam is critical because a horse can improve with a few days of rest after the owner notes a lameness or performance decline. "Such mild lameness issues may be best re-examined after a day or two of exercise," Mitchell added.

During a lower limb lameness exam, Mitchell said he likes to observe the horse in its stall first and then watch it walking out onto different footing. He looks for indications in the stall of discomfort, such as a hole or mound where the horse has created his preferred standing position. Then what does he look for when the horse walks out onto different footing?

Then Mitchell suggested that the examiner step back and look at the horse’s body symmetry, musculature, and posture. “There should be a thorough and complete exam overall, including a neurologic evaluation, not just an exam of the lame limb," he said. "All limbs, the axial skeleton, and musculature should be examined.”

He said this should include palpation as well as passive flexion (where the veterinarian flexes a joint to see if it has normal range of motion) and stress flexion (holding a joint in flexion for about a minute before watching the horse jog off) tests. With flexion testing, he looks to see if the horse is intolerant and/or if he is more lame following the flexion.

For the movement evaluation, Mitchell said he likes to observe the horse at both the walk and trot, in hand on straight lines, in circles or figure eights, and on a slope. He watches the horse move freely on the longe line over a firm surface, as well. Mitchell cautioned against this step, however, in a very lame horse. If the horse is unruly during any of these portions of the exam, Mitchell suggested administering a very small dose of the sedative detomidine to help control the horse without providing pain-relieving effects. He recommended watching the horse move under saddle, when possible, as a rider's weight often makes subtle problems more apparent. This is also a good opportunity to observe the horse at canter and how he performs his lead changes.

Once the examiner identifies the lame limb, he or she should assess hoof symmetry and configuration carefully. Further workup includes using other diagnostic techniques: hoof tester exam, wedge tests to stretch the deep digital flexor tendon (DDFT) or collateral ligaments (in which the examiner places a "wedge" under the foot to stretch either the DDFT or collateral ligaments, and watches for increased resultant lameness associated to the structure in question), diagnostic nerve blocks, and imaging modalities.

Before beginning diagnostic nerve blocks, Mitchell said, “Make sure the horse isn’t warming out of its lameness. Also, be mindful of show schedules and drug rules before using regional anesthesia.”

If the horse shows signs of overt swelling, significant pain on palpation, and/or decreased range-of-motion, the veterinarian might elect to skip straight to imaging rather than putting a horse through an unnecessary battery of movement tests that could exacerbate a significant problem.

In summary, Mitchell said veterinarians should “take the time to properly diagnose with powers of observation, a thorough exam with limb manipulations and exercise, and use diagnostic tools and imaging techniques to arrive at an accurate diagnosis."

About the Author

Nancy S. Loving, DVM

Nancy S. Loving, DVM, owns Loving Equine Clinic in Boulder, Colorado, and has a special interest in managing the care of sport horses. Her book, All Horse Systems Go, is a comprehensive veterinary care and conditioning resource in full color that covers all facets of horse care. She has also authored the books Go the Distance as a resource for endurance horse owners, Conformation and Performance, and First Aid for Horse and Rider in addition to many veterinary articles for both horse owner and professional audiences.

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