Caudal heel pain refers to lameness associated with the heel region of the foot. In the past many of these cases were lumped under the blanket term "navicular disease" which implicated the navicular bone as the primary source of pain.
We now know that this pain can arise from any number of structures in the caudal half of the foot. Pain can be related to the navicular bone, any of its soft tissue attachments, the navicular bursa or the deep digital flexor tendon. It can also be related to bruising or bone pain associated with a negative palmar angle of the coffin bone.
Diagnosis is usually made using local anesthesia and radiology. Advanced imaging, such as MRI, may be required to pinpoint the specific structure of interest. There are a number of different shoeing options available to these horses. Some shoes decrease strain on the deep digital flexor tendon while others focus on concussion relief. While there may be similar principles for approaching these cases, a good lameness examination is critical to choosing the right shoeing plan.
The palmar angle refers to the angle that the solar (bottom) surface of the coffin bone makes relative to the ground. When the toe is lower than the heels this is referred to as a "positive" palmar angle. When the heels are lower than the toes this is a "negative" palmar angle.
The hoof pastern axis or the alignment of the pastern bones relative to the coffin bone can be affected by this as well. A negative palmar angle can be associated with a "broken back" hoof pastern axis. This in itself can cause lameness because it puts more stress on the joints of the distal limb. A negative palmar angle can also be responsible for pain and pressure in the heel of the foot, especially if the horse is lacking in sole depth.
Addressing the cause of the negative palmar angle requires an evaluation of the external structures of the foot relative to the bones of the distal limb. There are a variety of shoeing options available depending on each individual case.
Some horses may require specially designed shoes whereas others can be managed with a trim.