Sidebone is a common condition of

horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million yea ...

s, characterized by the

ossification Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. There are two processes resulting in ...

of the collateral cartilages of the

coffin bone The coffin bone, also known as the pedal bone (U.S.), is the bottommost bone in the front and rear legs of horses, cattle, pigs and other ruminants. In horses it is encased by the hoof capsule. Also known as the distal phalanx, third phalanx, ...

. These are found on either side of the foot protruding above the level of the coronary band. The lateral cartilages support the hoof wall and provide an important role in the support and cushioning provided to the heel. The front feet are most commonly affected.

Causes

Repeated concussion of the foot is probably the cause in many cases. Such concussion could be produced when a horse is always worked on a hard surface. There also appears to be a hereditary component to sidebone but this may be because bad conformation is hereditary and bad conformation appears to predispose to sidebone. Bad conformation would include * those with narrow, upright feet * those with unbalanced feet, especially if they have toe-in or toe-out conformation *

draft horse A draft horse (US), draught horse (UK) or dray horse (from the Old English ''dragan'' meaning "to draw or haul"; compare Dutch ''dragen'' and German ''tragen'' meaning "to carry" and Danish ''drage'' meaning "to draw" or "to fare"), less oft ...

s, or horses with a heavy build, are more likely to develop sidebone than light horses or ponies

Symptoms

Sidebone may be associated with

lameness A limp is a type of asymmetric abnormality of the gait. Limping may be caused by pain, weakness, neuromuscular imbalance, or a skeletal deformity. The most common underlying cause of a painful limp is physical trauma; however, in the absen ...

but many horses with sidebone are not lame. It follows that sidebone often gets blamed for being the cause of lameness when there is actually another cause.

Diagnosis

Careful examination of the collateral cartilages by

palpation Palpation is the process of using one's hands to check the body, especially while perceiving/diagnosing a disease or illness. Usually performed by a health care practitioner, it is the process of feeling an object in or on the body to determine ...

can give a good indication that they are solid and bony rather than firm, springy cartilage. Usually, however, sidebone is found accidentally when the foot is radiographed, as sidebone has few outward signs in most cases. In mild cases, there are small areas of calcification; more advanced cases will have ossification of the entire cartilage. Rarely, severe lameness can be caused by fracture of an ossified cartilage, or by ossification which deviates enough to impinge on the short pastern bone.

Treatment

Sidebone usually does not cause any problems, but when it does it is difficult to treat. Box rest and

Non-steroidal anti-inflammatory drug Non-steroidal anti-inflammatory drugs (NSAID) are members of a therapeutic drug class which reduces pain, decreases inflammation, decreases fever, and prevents blood clots. Side effects depend on the specific drug, its dose and duration of ...

s such as bute may be useful. In some cases the only useful treatment is a

neurectomy A neurectomy is a type of nerve block involving the severing or removal of a nerve. This surgery is performed in rare cases of severe chronic pain where no other treatments have been successful, and for other conditions such as vertigo, involuntary ...

of the palmar digital nerves.

Prognosis

Many horses compete actively in demanding sports with sidebone, and are not hindered in any way. If the ossification is severe and associated with lameness then the prognosis is more guarded. Discovery of sidebone on an equine prepurchase exam without signs of lameness or local sensitivity should not affect the purchaser's opinion of the horse.

Sources

*{{Cite book, author=King, Christine, BVSc, MACVSc, and Mansmann, Richard, VDM, PhD , title=Equine Lameness , publisher=Equine Research, Inc , year=1997 , pages=689-691 Equine injury and lameness