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just below the distal interphalangeal articulation, and is found in the caudal aspect of the foot, starting from around the centre of the distal interphalangeal articulation and extending back to the bulbs of the heels along the palmar process of the distal phalanx. It exits the hoof capsule approximately two-thirds back from the front of the hoof capsule towards the bulbs of the heel and can be manipulated externally (Fig 3).


Sidebone is the ossification of the cartilages of the foot. It can be found medially, laterally, or biaxially, but is most commonly found laterally (ruohoniemi et al 1997). It is thought that the majority of mature horses will have some form of ossification/calcification of the cartilages in the foot, although these may be minor and never effect the health or performance of the animal. The ossifications/calcification most commonly start at the junction where the cartilage joins the distal phalanx. It can also less commonly be found as separate centres of ossification within the cartilages. It is the author’s understanding that if the sidebone starts from the junction between the cartilage and the distal phalanx, this can be classified as ossification. If there are separate centres of ossification, this is actually the formation of calcium salts that can be found anywhere within the lateral cartilages of the foot and therefore should be referred to as calcification.

Sidebone is diagnosed with aid of a palmar nerve block and radiographs (x-rays), although if the sidebone is in the early stages of formation, that is in the first six weeks, it may not be identifiable by x-ray imaging due to a lack of density of the ossification (Fig 4).

indicator as it is only present in more extreme cases and is not always present in the early stages.

Many equine professionals believe that sidebone is not a cause of lameness but is a symptom of the imbalance that is the primary cause of lameness. In the author’s opinion, sidebone cannot be discarded as a cause of lameness. When the sidebone is forming at the junction with the distal phalanx, which is the most common location for the start of formation, the ligaments that attach the cartilages to the distal phalanx can be affected causing lameness. This is backed up by the findings of Dyson and nagy (2011) who thought these to be contributing factors in the cause of lameness of horses with sidebone. There is a growing body of evidence that uniaxial and biaxial ossification of the cartilages of the foot should not be dismissed as a cause of lameness, and this is a subject for debate among hoof care professionals. either way, the gait of horses with sidebone is often affected and the correct treatment by the farrier can help to alleviate these symptoms.

If there are separate centres of ossification forming - depending on the location and shape of the ossification - when the hoof flexes, a pressure point can form a causing pain on movement, although this form of sidebone is less common. Where bilateral sidebone is present there is less effect on hoof morphology; there may only be a change in appearance if one side is affected more than the other. These horses often show a shortening in the stride having a ‘pottery’ gait, as opposed to a lateral sidebone case that shows lameness on the turn or uneven ground. however, this is not always the case as some bilateral sidebone cases have more ossification on the lateral side and so show some of the symptoms of lateral sidebone.

CAuSeS oF SIDeBone

FIgure 4. exAMple oF x-rAy oF BIlATerAl SIDeBone

one of the main causes of sidebone is excessive concussion, often in a specific area such as the lateral branch of the foot. excessive concussion can be due to conformation, work or poor fitting shoes or unbalanced trimming (ruohoniemi et al 1997). holm et al (2000) found that sidebone can also be hereditary. The uneven distribution of concussive forces within the hoof cause the lateral cartilages to have to work harder to help with dispersion of concussion, which is considered to be important in the dispersion of concussion (Balch et al, 1991).

In most cases, the sidebone formation is only on the lateral side, and in these cases the hoof morphology can change. The lateral heel and quarter become more upright and has a shunted appearance. These cases tend to show lameness on uneven ground conditions and/or on a tight turning circle. The cartilages are mainly within the hoof capsule but some do protrude above the coronary band and if they are ossified they can be palpated (Fig 3). however, this is not a reliable diagnosis


The common conformation that is susceptible to sidebone is a toe-in or base narrow conformation (Stashak 2002). This conformation affects the distribution of concussion within the hoof and loads the lateral aspect of the hoof excessively; this often results in a lateral sidebone. gait can also have an effect on the likelihood of getting sidebone, such as if a horse has a high knee action causing the hoof to land with a increased impact (Dyson and nagy 2011). This higher action increases the amount of concussion to which the hoof and, in turn, the lateral cartilages have to dissipate.

Forge | August 2015

FIgure 5. A ConCAVe Shoe ShoWIng A ChAMFereD lATerAl BrAnCh

The fitting of the shoe and balance of the hoof also can have an effect upon the distribution of concussive forces. If the shoe is not balanced or is placed incorrectly this causes an imbalance in the distribution of concussive forces on the hoof. This is also the case if the hoof is trimmed unbalanced and the longer side of the hoof comes into contact with the ground sooner than the shorter side. loading one side first puts the lateral cartilage on the longer side under more load. The effects of shoe fit or trimming often takes several sets of shoes to cause a long-term problem as the hoof is a flexible structure and is good at coping with mistakes in the shoeing process.

The other cause of sidebone is direct trauma; this can be a direct blow to the lateral cartilages or surrounding areas or by a lesion in that area. In both cases there is usually a more primary injury to be dealt with first and the sidebone develops as a secondary issue.

TreATMenT oF SIDeBone:

Most text books available to farriers and apprentices refer to the traditional sidebone shoe (hickman and humphrey 1988, Colles et al 2010), this shoe was designed many years ago when the majority of horses that contracted sidebone were of the heavier breeds, these breeds are more susceptible to sidebone but they are less common these days. They also only look at the treatment of one form of sidebone (lateral sidebone). The sport horse; which includes hunter, riding club and eventers, is more commonly affected by sidebone today and so has to be shod in a different way with different considerations.

The traditional sidebone shoe (Figure 1) is made from a heavy flat section and is plain stamped with a chamfered lateral branch on the ground surface from the toe around to the heel. The chamfered lateral branch facilitates the change in gait on horses with sidebone on the lateral side. These horses’ gaits change in that the affected limb flights towards the opposite limb and then lands hard on the lateral aspect. The chamfer on the lateral branch allows the hoof to come under the limb more before it starts to load, aiding with loading the limb more equally mediolaterally. The lack of fullering in the shoe allows the shoe to slide across the ground with minimal resistance and aid the hoof to get under the limb more before loading. These heavy horses were typically working on harder surfaces and with the

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