Sidebone is a common condition of horse

Horse

The horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...

s, characterized by the ossification

Ossification

Ossification is the process of laying down new bone material by cells called osteoblasts. It is synonymous with bone tissue formation...

 of the collateral cartilage

Cartilage

Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...

s of the coffin bone

Pedal bone

The pedal bone, commonly known as the coffin bone , is the bottommost bone in the equine leg and is encased by the hoof capsule. Also known as the distal phalange, third phalange, third phalanx, or "P3"....

. 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
  Equine conformation
  Equine conformation evaluates the degree of correctness of a horse's bone structure, musculature, and its body proportions in relation to each other. Undesirable conformation can limit the ability to perform a specific task. Although there are several universal "faults," a horse's conformation is...
  
  
• draft horse
  Draft horse
  A draft horse , draught horse or dray horse , less often called a work horse or heavy horse, is a large horse bred for hard, heavy tasks such as ploughing and farm labour...
  
  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

Lameness (equine)

Lameness in horses and other equidae is a term used to refer to any number of conditions where the animal fails to travel in a regular and sound manner on all four feet...

 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

Palpation is used as part of a physical examination in which an object is felt to determine its size, shape, firmness, or location...

 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

Radiography

Radiography is the use of X-rays to view a non-uniformly composed material such as the human body. By using the physical properties of the ray an image can be developed which displays areas of different density and composition....

, 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 drug

Nonsteroidal anti-inflammatory drugs, usually abbreviated to NSAIDs or NAIDs, but also referred to as nonsteroidal anti-inflammatory agents/analgesics or nonsteroidal Anti-inflammatory medicines , are drugs with analgesic and antipyretic effects and which have, in higher doses, anti-inflammatory...

s such as bute

Phenylbutazone

Phenylbutazone, often referred to as bute, is a non-steroidal anti-inflammatory drug for the short-term treatment of pain and fever in animals. In the United States, it is no longer approved for human use.-In humans:...

 may be useful. In some cases the only useful treatment is a neurectomy

Neurectomy

Neurectomy is the surgical removal of a nerve or a section of a nerve. This procedure may be performed, for example, in cases of chronic pain where other treatments have failed. However the removal of the nerve can also cause negative effects, such as permanent numbness...

 of the palmar digital nerves.

Prognosis

Prognosis

Prognosis is a medical term to describe the likely outcome of an illness.When applied to large statistical populations, prognostic estimates can be very accurate: for example the statement "45% of patients with severe septic shock will die within 28 days" can be made with some confidence, because...

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

Equine prepurchase exam

When buying a horse, many buyers ask for an equine prepurchase exam. This serves to identify any preexisting problems which may hinder a horse’s future performance and reduce buyer risk...

without signs of lameness or local sensitivity should not affect the purchaser's opinion of the horse.