Page 300 - The Veterinary Care of the Horse

Lameness from coffin joint pain is relatively common in the forelimbs, but it can also be a

cause of hind limb lameness. It may be sudden or gradual in onset and affect one or both
VetBooks.ir limbs. It is often more obvious when the horse is worked in a circle, especially on a hard
surface. If the disease is bilateral, the horse may shorten its stride or lose its enthusiasm for

jumping, rather than demonstrating obvious lameness. In most cases, the disease is more
advanced in one limb and lameness is apparent.

The joint capsule is often distended. A swelling may be seen just above the coronary band
at the front of the foot. If the joint is flexed or rotated, the discomfort may cause the horse to

snatch the foot away. The lameness may be exacerbated by a flexion test.

Predisposing causes

Horses with mediolateral foot imbalance are predisposed to strains and degenerative changes
of the coffin joint. When the horse is working, most of the joint movement is flexion and
extension. If the foot is unbalanced, however, the joint is tilted from side to side and this puts

more strain on the supporting ligaments and joint capsule.

Long-toe, low-heel conformation or an abnormal angle of the pedal bone within the hoof
capsule also increase the wear and tear of the coffin joint.

Traumatic injuries such as acute sprains can also contribute to coffin joint pain.

Diagnosis

It is not always easy to confirm that the coffin joint is the source of pain and the results of
nerve blocks and radiographs have to be interpreted with care.

NERVE BLOCKS

Injection of local anaesthetic into a painful coffin joint rapidly improves the lameness.
However, in some horses, the local anaesthetic can also eliminate pain arising from other
areas of the foot, including the navicular bone and navicular bursa. As a general rule, if the

horse responds quickly to intra-articular analgesia but does not improve with analgesia of the
navicular bursa, the coffin joint is considered to be the source of pain.

RADIOGRAPHY

Several views of the foot must be taken and the images have to be interpreted with care. It is
possible for there to be remodelling of the bone close to the joint, giving the appearance of

degenerative joint disease (DJD), but without any pain. The horse may also experience
significant joint pain in the absence of any radiographic changes.