Recognizing, Evaluating & Understanding Hoof Distortions and How it Relates to Lameness

There are many common factors connected with lower limb lameness (LLL). Horses that are driven or ridden in a straight line are less affected by lower limb lameness than those horses who are asked to continually and repeatedly turn circles and make complicated lateral movements. Endurance horses, light driving horses and general pleasure horses in general exhibit fewer instances of lower limb lameness as compared to performance horses (roping, reining, cutting and barrels), dressage horses, and hunters and jumpers. Similarly, horses that are not confined to stalls and are not limited in their exercise are also less affected by LLL than horses that are confined to stalls, regardless of how they are shod. This does not mean that lameness is absent in this active group of horses that go in a straight line, however I believe there are correlations to the instances of lower limb lameness, and the activity (conditioning) and lateral movement requirements of horses. I can remember back 40 and 50 years ago where the existence of lameness was minimal compared to the percentage of cases today. I believe that is largely due to the fact that horses were ridden much harder and much more frequently than they are today and usually traveled in straight paths, with the exception of the rodeo stock. Rarely were horses confined to stalls or even small paddocks, and many horses were actively used without shoes and were self-maintained for the most part. Never the less, times have changed and the role that horses play in people’s lives have changed. Limited space and activity, as well as an increase in the frequency and severity of lateral and circular movements are the changes that contribute the occurrence of lower limb lameness. The question is, has or can the hoof care parameters being used address the current demands placed upon the horse to overcome LLL or better yet prevent LLL from happening in the first place.

There are several factors to consider when determining if the hoof care principles being employed are adequate and/or beneficial for a particular horse. Assessing the needs of the horse in terms of discipline, terrain, frequency of use, level of activity, current condition of the hoof (foot function), and the presence or absence of lameness must all be considered. Other aspects of hoof care that have probably not received enough consideration in the past, but are now proving to be real keys in both treating and preventing lameness is leverage and hoof distortion.

LEVERAGE

Like every structure that is in motion, the foot and lower limb are always subject to some sort of leverage. It is designed to be able to tolerate a certain amount of leverage from front to back, however when the leverage becomes greater than what is “normal” then structures begin to fail. The most vulnerable structure affected by excessive leverage is the distal interphalangeal joint (coffin joint). In the wild, horses are not asked to repeatedly make sharp turns or engage in constant circles, yet they will wear away as much of the outer hoof wall as necessary in all direction to minimize the leverage to the DIP joint. The harder the terrain, the more the wall is worn away to bring the pivoting points of the foot more towards the center of the foot.[1] In a softer environment, the hoof wall does not need to wear as much because the ground will yield to the hoof wall. My point is that leverage is being reduced much greater than what is conventionally provided for our domestic horses, and the wild horses in general are going in a straight line and don’t have the added weight of a rider and tack. We need to start thinking about leverage and using some common sense about how we prepare the feet and what we apply to the foot, and how that affects what we ask the horse to do. As mentioned earlier, many horses today are constantly going in circles, either in exercise, training or in the discipline they perform. It is good that many of the arenas that horses compete in have footing that will partially yield to the foot and allow for some leverage reduction. However, you cannot depend upon the surface to provide enough leniency for the DIP joint, so the hoof care provider needs to address the leverage, and it needs to start with the preparation of the hoof. That is where being able to recognize hoof distortion is such a key. Hoof distortions are either directly or indirectly the cause of most of the undue leverage to the DIP joint. It has become obvious that the longer, distorted toe directly increases the leverage at the time of breakover, which increases the effort and strain on the DIP joint. Distortion of the heels is more indirectly increasing the leverage, because they can push the toe forward or cause diagonal toe-quarters to flare. And finally, distortions of the bars and frog all offer insight to distortions that exist in other parts of the foot. Pain in the frog or bars can also force the horse to use another part of the foot to land, usually the toe which will perpetuate further problems. Distortion and leverage is a big deal, and if you only get one thing from this lecture, that would be it.

HOOF DISTORTION

In general, hoof distortion is any growth, presence or lack of presence a hoof structure possess that interferes with the proper function of the foot. For example, hoof capsule distortion is basically any amount of hoof wall that has grown beyond the level of live, functional sole and frog. The hoof capsule, although hard and brittle, can become twisted, bent, shifted and manipulated around the coffin bone. Extra length or growth in a direction that forces it out of its normal position will cause areas of the hoof wall to collapse or fail under the undo stress. For example, if the heels become too tall or long and driven forward due to the angle at which they grow, they take on weight that they were not intended to. If this happens, they often become crushed and lack good support quality. As the heels grow in excess of the functional sole, they become more curved the further forward they grow. The forward growth of the heels causes the bars to become more bent as well. Excessive curvature, cracks and bruising in and around the bars are all examples of bar distortions. The frog on the other hand can become atrophied and becomes weak as the heels and the hoof wall grow beyond the level of the sole. If the toe is distorting forward at the same time, it will pull the frog apex forward as well, causing the tip of the frog to become long, narrow and pointed. All of these structures can offer insight into hoof distortions that can mean extra leverage and stress to the internal components of the foot and ultimately lead to lameness. Therefore, being able to recognize and eliminate even the most subtle hoof distortions will help keep you ahead of the curve in preventing lameness or give you good direction when treating lameness.

E.L.P.O. HOOF EVALUATION PROTOCOL

Equine Lameness Prevention Organization has established a standard set of guidelines and principles that promote proper foot function in horses. Foot function is described as all of the structures of the hoof working together in equilibrium or balance around the DIP joint. Hoof distortions cause stress in and around the DIP joint and therefore become a focus for hoof care maintenance in order to establish balance. Through the cooperation of the directors and members of the Equine Lameness Prevention Organization, we have helped develop some guidelines on evaluating feet. The goal of the E.L.P.O. Hoof Evaluation Protocol is to accurately, consistently and in accordance with an established standard be able to determine the amount and/or location of hoof distortions in individual equine feet. Although an overall rating for each foot may be achieved, individual attention to primary hoof structures is the key. Through the systematic evaluation of the external hoof anatomy, a more accurate and meaningful assessment of the foot can be achieved, as well as a determination of the overall health and soundness of the horse. To give you a general idea of what each number rating means, we have listed a short explanation of each rating.

#0: Considered to be a perfectly natural, normal foot, free of hoof distortions, and is expected to be functioning at its optimum efficiency. Hoof structures with this grade would also be representative of a foot that either requires no maintenance or has just been trimmed and/or shod, and again is free of hoof distortions.

#1: Indicative of a natural normal foot that is at the end of a trimming/shoeing period and requires basic maintenance. Minor hoof distortions seen are the result of normal growth and with basic maintenance will be returned to a #0 status. If a #1 status is achieved after trimming/shoeing, then this grade would be representative of hoof structures that possesses only minor hoof distortions that would still allow the foot to function efficiently.

#2: Feet or Hoof Structures with a #2 grade have hoof distortions that can start to affect proper foot function. Although these are commonly seen at the end of a shoeing cycle, this rating is indicative of distortions that generally were not fully dealt with at the beginning of the shoeing/trimming cycle. Feet and structures in this condition can start to negatively affect performance, but may not be recognized as problems by everyone.

#3: Feet or Hoof Structures with a #3 grade have hoof distortions that can cause minor to moderate lameness issues. Foot function is often being compromised and common gait faults such as stumbling, forging and landing toe-first are prevalent, and signs of coffin joint pathology may be recognized and even diagnosed by veterinarians. Feet or Hoof Structures with a #3 rating are challenging the soft tissue around the DIP joint.

#4: Feet or Hoof Structures with a #4 grade have moderate to severe hoof distortions that are often associated with serious lameness issues. Feet or Structures with a #4 rating have been subject to long term hoof distortion and often, irreversible damage can occur. Foot function can be at least somewhat restored with shoes, pads, and detailed hoof trimming.

#5: Feet or Hoof Structures with a #5 grade have the most severe hoof distortions that contribute to both soft tissue and bony damage. Horses are often severely lame or debilitated as a result of the distortions. A #5 rating is sometimes irreversible, but can be improved with the use of various prosthetics and more detailed hoof preparation.

In general, the hope is that through following the guidelines of E.L.P.O. Hoof Care, veterinarians and farriers will be able to effectively lower each hoof distortion rating by 1 or possibly 2 points through their hoof trimming. Some structures like the frog may take several trimming or shoeing cycles to realize an appreciated improvement, where other structures like the heels, bars and toe will commonly yield the most instant results. In short, the more structures of the foot that are brought to a #0 to #1 distortion rating, the more positively it will affect those structures that need time to respond. Either way it is important to know that you can recognize when something is not right and then be able to have some tools to know that you can either fix it or at least make an improvement.

References

[1] Ovnicek G, Erfle J, and Peters D. Wild horse hoof patterns offer a formula for preventing and treating lameness. Proceedings, Am Assn Eq Prtnrs 1995; 41: 258-260