When offering arthritic horses relief, start from the ground up
The degenerative joint disease arthritis is all too common in active and aging horses. In an effort to slow the progressive deterioration of joint tissue, owners and veterinarians often reach for anti-inflammatory medications and/or regenerative therapies. After all, our goal is to keep these joints comfortable.
One often-overlooked strategy in this effort is hoof care. Certain trimming and shoeing techniques can alter a horse’s limb biomechanics—for better or worse. In this article we’ll discuss how to care for arthritic horses’ hooves for maximum comfort.
What Exacerbates Joint Pain?
Arthritic horses try to minimize their joint pain by reducing the load on the affected limb(s) and shortening stride length. “This suggests that pain is associated with the concussion of impact and extreme ranges in motion (ROM),” says Andrew Parks, DVM, Vet MB, MRCVS, Dipl. ACVS, a professor at the University of Georgia’s College of Veterinary Medicine, in Athens.
Force of impact
The limb’s loading rate (deceleration) when the foot lands affects the force of impact on that leg, as can footing type. “The impact of baked clay in summer or frozen ground in winter is quite different from a soft dirt paddock, bedded stall, or engineered arena,” says Parks. “Anything that slows down the rate of deceleration of the foot is likely to decrease the effect of impact. Materials that absorb energy on hoof landing—either from the ground surface or within the shoeing apparatus—also reduce impact.”
Range of motion
You’re probably already familiar with this concept: Your veterinarian maximizes a joint’s range of motion when he or she performs a diagnostic flexion test to pinpoint soreness in a painful joint. Excessive flexion or extension/dorsiflexion (backward bending or bowing) can aggravate arthritis.
Owners and farriers should handle arthritic horses’ legs with care. “Check range of motion and flexion ability, and don’t force an arthritic horse to bend or flex its limbs beyond its comfort zone,” says Steve Kraus, CJF, resident farrier and instructor at Cornell University’s College of Veterinary Medicine, in Ithaca, New York. “Use of a foot stand (when trimming or shoeing) keeps hind limbs low and supports the front legs to provide better comfort for both horse and farrier.”
To modify or limit range of motion extremes in locomotion, Parks recommends farriers help the foot lift and roll over (called breakover) more easily. “This may mean not only rolling the toe but also the whole perimeter of the shoe and even the heels,” he says. The easier it is for the horse to lift his heels off the ground, the less dorsiflexion the foot will experience at breakover.
Hoof balance is key to keeping an arthritic horse comfortable. Create a more level landing surface by picking out gravel and other debris from hooves daily. Have the feet trimmed every four to seven weeks (depending on hoof growth rate) to help balance the hooves and reduce the horse’s risk of developing long toes and collapsed heels, which can make him more likely to stumble.
“Farriers can manage the hoof capsule with trimming and shoeing to provide proper limb alignment so that forces are distributed equally through the joints,” says Kraus.
If a foot is acutely imbalanced (say, for example, one side has been wedged or trimmed shorter than the other), the joint on the elevated side of the hoof will narrow—something that’s visible on radiographs (X rays) taken immediately following this practice. “However,” says Parks, “if you look at feet with obvious (chronic) coronary band asymmetry and hoof imbalance, an interesting finding is that the imbalance in the joint space usually is not evident on radiographic images.”
This compensatory phenomenon is related to the coffin bone’s movement relative to the hoof capsule. The hoof’s growth rate also changes, slowing on the side experiencing the greater load.
Parks reminds us that the same principles that encourage bone remodeling might also apply to other tissues. Overloading on one side of the hoof might, in fact, slow the rate of cell replication in the coronary band on that side.
“If the hoof wall is imbalanced side-to-side (uneven hoof wall height between medial and lateral—inner and outer—sides), then theoretically, unequal overload stresses can create degenerative joint disease (DJD),” says Parks. “However, a horse’s natural compensatory hoof mechanisms tend to minimize changes within the joints. You may have appreciated how quickly the hoof capsule changes shape once a horse shoe is removed—usually within 24 to 48 hours.”
That said, he points out that if mediolateral imbalance within the foot’s internal structures persists, a horse can develop DJD. Uneven forces place undue pressure on joint components, especially cartilage, which can then create or exacerbate joint deterioration and arthritis, adds Kraus.
Genetics and/or inappropriate trimming can also create dorsopalmar (front to back) imbalances, which affect the hoof-pastern axis (when correct, the front hoof wall should be parallel to the pastern angle).
When trimming and shoeing for balance, one of the farrier’s main goals is to make sure the foot is placed properly beneath the skeletal column, says Kraus. “Caudal (rear) heel support relies on supporting the heels in their proper location beneath the leg,” he says. “This support is important to minimizing arthritic discomfort. As the hoof first strikes the ground, the heels act as a fulcrum. If positioned too far forward under the limb, the leg tends to rock backward on that point of the heels. The horse must exert muscular force to overcome this, which strains the joints. Proper heel support requires trimming the hoof to the widest, highest, rearmost area of the frog. If that cannot be done, it is possible to provide support with shoeing.”
To align the heel properly, farriers usually fit the horse with an appropriately sized shoe that increases the hoof wall’s surface area contact with the ground, says Kraus. This prevents rocking back on the heels or sinking into soft ground, either of which stress joints whether they’re arthritic or healthy.
Farriers might apply egg bar shoes to horses with low-angled, underrun heels, says Kraus. “Caudal heel support from the bars (found at the rearward ends of the hoof wall) reduces backward sinking of the hoof, while also providing a greater bearing surface to spread out the horse’s weight,” he says.
Parks says elevating the heels has been shown to alter the distribution of pressure in the coffin joint, which could potentially increase wear and tear.
“The ideal relationship between the pastern and the hoof is when the dorsal (front) wall of the hoof is parallel to the dorsal pastern, and if the foot is trimmed so that this relationship is not parallel, it has the potential to increase the overall force on the foot during the course of the stride,” says Parks. “Additionally, a long toe increases the lever arm at breakover, which increases the force required to lift the heels off the ground. These phenomena exacerbate arthritic pain in the distal (lower) joints.”
Kraus adds that when horses strain to move their lower limbs and break over a long toe, they can aggravate low or high ringbone (coffin or pastern joint arthritis).
Smart Trimming & Shoeing Techniques
Backing up the toes
Many farriers attempt to correct a long-toe, low-heel hoof configuration by setting the shoe back at the toe. While Parks says this improves breakover for the short-term, leaving the toe hanging too far over the toe of the shoe means the wall at the toe is not in direct contact with the shoe. Therefore, it receives less mechanical stimulation than the wall that is in direct contact with the shoe from the toe-quarter junction (pillars) to the heels. “This affects the way the wall grows,” he says, reminding us that the wall under greater stress will grow slower and vice versa. “Biofeedback tries to restore a previous state,” he says.
Kraus says farriers often apply rocker or rolled toe shoes to horses with arthritic conditions. “These shoes artificially shorten the distance and, hence, the leverage in front of the center of rotation on the foot beyond what can safely be trimmed away,” he says. “Sound, properly trimmed horses need normal toe length for optimum propulsion, but horses with arthritis in their lower joints do better with less-than-normal leverage (i.e., shorter toes).”
Parks says he’s a fan of rocker and roller shoes but warns against removing too much dorsal hoof wall in the shoeing process. “If the farrier uses a rasp to gradually thin the wall at the toe, it may not change hoof wall growth, provided enough stiff wall (the outer one-third to one-half of the wall) is left in contact with the shoe,” he says. “In contrast, if the toe wall is chopped away at a 45-degree angle, while this may ease breakover so that the dorsal wall isn’t in contact with the shoe, it isn’t under as much stress as the adjacent wall. Therefore, on the reasonable assumption that wall under less stress grows faster, the toe will outgrow the adjacent wall, thus changing the conformation of the foot, which may add to arthritic pain.”
Protecting the hind limb
Most shoeing practices only have a direct effect on the lowest limb joints—the coffin and pastern joints. However, farriers do attempt shoeing strategies to influence higher joints, such as using lateral extensions or egg bar shoes on the rear hooves of horses with distal hock arthritis (bone spavin). Kraus says a lateral hind shoe extension provides support to prevent a base-narrow horse’s hocks from rotating outward, while an egg bar shoe might reduce excessive hinge motion that otherwise stresses hock joints.
Study results, however, show that neither rear-foot lateral extensions nor egg bar shoes have a significant effect on stabilizing affected hock joints.
Then there are trailers (or caulks) on hind shoes, which some veterinarians and farriers argue against using because they can cause a foot to stick and torque the joints. Their use, however, often depends on the equestrian activity and terrain conditions.
Traditionally, farriers have applied pads beneath shoes to provide sole protection and shock absorption. Kraus says that in his experience, polyurethane pads provide limited shock absorption and are better suited simply for sole protection. Leather pads do improve shock absorption but deteriorate over time, he says.
“Some synthetic pads are designed to absorb shock; however, with only 1/8-inch of material on a 1,000-pound (or more) horse, how much shock can really be absorbed?” he says. “A pour-in pad or packing a shoe with synthetic gel may be a better option to achieve shock absorption” for arthritic horses. These materials conform to the sole and frog for a more uniform distribution of shock absorption throughout the hoof.
Considering shoe weight and type
Any type of shoe on a horse’s foot adds weight that the animal must lift from the ground at breakover. To reduce shoe weight, try applying aluminum shoes, which are one-third the weight of steel, says Kraus. “Or, an alternative to bar shoes is the Myron McLane pad that includes frog and heel support,” he says. Wide web shoes are another support option and weigh less than egg bar shoes.
Synthetic shoes—nonmetal or a metal composite with nonmetal materials—absorb the most shock. You can choose from many types of those shoes, both nail-on and glue-on. Remember, however, that plastic materials can be slippery on wet grass or ice and might wear more quickly than steel shoes. “With arthritic horses, it’s a delicate balance between slip and grip,” says Kraus.
Barefoot or Shod?
“Leaving a horse barefoot is generally good, particularly in a nonperforming horse with arthritis,” says Parks. “In most cases, the unshod hoof capsule provides the best damping to assimilate the shock of foot impact. And, a barefoot horse is able to ‘roll’ its own hooves through natural abrasion.”
“When barefoot arthritic horses wear their hooves to their comfort level, this shouldn’t be confused with conformational defects that often wear the hoof in the opposite direction than the horse needs,” says Kraus. However, “barefoot horses with thin soles may become sore-footed and then alter their gait in such a way to strain arthritic joints.”
Still, barefoot advantages might outweigh disadvantages to help curb arthritic pain, and owners can apply hoof boots for riding or navigating rough terrain, if needed. Our sources recommend using a lightweight boot with built-in breakover and adding a viscoelastic pad inside.
Before making trimming and shoeing changes, have your veterinarian perform a thorough diagnostic work-up of your horse’s lameness problem. Ask him or her take radiographs to visualize the angles of internal hoof structures, the extent of osteoarthritis in a joint, and the depth of sole a farrier has to work with.
“Shoeing methods for arthritic horses ideally incorporate ways to transfer motion to the ground instead of to painful joints,” says Kraus.
“Shoes modified properly to help with arthritic problems may be a more permanent way to manage some horses with arthritis,” says Parks. “Trimming and shoeing practices are useful adjuncts to multitreatment modalities that include joint injections, non-steroidal anti-inflammatories, IRAP (interleukin-1 receptor antagonist protein), and in some cases regenerative therapies.”
There is no single trimming or shoeing recipe that farriers can apply to every horse. Following basic principles of balancing the foot, easing breakover, supporting the heels, and aligning the hoof-pastern axis provide the best foundation for both normal and arthritic horses.