TOBA: Thoroughbred Owners and Breeders Association
Owner Education

Unsoundness and Blemishes: Hind Legs

Illustrations courtesy of the American Youth Horse Council's Horse Industry Handbook

An unsoundness is any defect in form or function that interferes with the usefulness of the horse. A blemish is an acquired physical defect that does not interfere with the usefulness of the horse, but may diminish its value.

Some common unsoundnesses of the hind leg are:

Knocked-down Hip - A condition where one hip is lower than the other when viewed from the rear. This condition is usually the result of a fracture at the point of one hip. Animals maybe serviceable, but probably will not be able to perform at a high level.

Stifle Lameness or Gonitis - Any inflammation of this large muscular joint structure. If the condition becomes chronic synovial joint inflammation or arthritis has occurred, recovery is poor. Early detection and removal of the strain increases the chances of a full recovery.

Stifled or Upward Fixation of the Patella - A type of stifle inflammation in which the patella locks and causes the leg to remain in an extended position. Young horses may outgrow the condition while older horses will need surgical intervention.

Stringhalt - An exaggerated lifting and forward motion of one or both hocks that is spasmodic and involuntary. It is particularly noticeable when the animal is backed up after the horse has been standing stationary for a period of time. A horse that is warmed up will usually walk out of the condition.

Curb - (See illustration at right.) A hard enlargement on the rear of the cannon bone immediately below the hock. It begins as an inflammation of the plantar ligament and the inflammation leads to a thickening of the ligament. Faulty conformation such as sickle and cow hocks are predisposing factors.

Capped Hock - This condition is one of the most common blemishes of the hind leg. It is a firm enlargement at the point of the hock that is the result of an inflammation of the bursa. It usually is caused by trauma to the hock.

Thoroughpin - Soft, fluid-filled enlargement in the hollow of the hock. The swelling can be pushed freely from the outside to inside of the hock. The blemish is caused by a strain to the flexor tendon that has allowed synovial fluid to escape from the joint capsule.

Bog Spavin - A soft distension on the inside front portion of the hock. It is caused by inflammation of the synovial membrane of the hock. Straight hocks, strain and rickets have been known to be causes. Bog spavins may be treated with some success by draining, corticoid therapy, firing or blistering.

Bone Spavin - (See illustration at right.) A bony enlargement on the lower interior surface of the hock that may result in limited flexion of the hock. Faulty hock conformation, excessive concussion and nutritional and hereditary conditions are predisposing factors.

Blood Spavin - A term that describes varicose veins in a horse.

Occult Spavin - A hock lameness without any visible signs. It is also known as a blind spavin. Prognosis is not good because they lead to chronic discomfort and pain.

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