|First Posted: Aug 16, 2009|
Jul 22, 2013
Ringbone is exostosis (bone growth) in the pastern or coffin joint of a horse. In severe cases, the growth can encircle the bones, giving ringbone its name. It has been suggested by some authors that such a colloquial term, whilst commonly used, might be misleading and that it would be better to refer to this condition as osteoarthritis of the inter-phalangeal joints in ungulates (Rogers and Waldron, 1995: 34-35).
Ringbone can be classified by its location, with "high ringbone" occurring on the lower part of the large pastern bone or the upper part of the small pastern bone. "Low ringbone" occurs on the lower part of the small pastern bone or the upper part of the coffin bone. High ringbone is easier seen than low ringbone, as low ringbone occurs in the hoof of the horse. However, low ringbone may be seen if it becomes serious, as it creates a bony bump on the coronet of the horse.
Causes of Ringbone
Excessive tension on the tendons, ligaments, and joint capsules of the pastern area can strain the periosteum. The body compensates by growing bone at the stresspoint. Strain on the extensor tendon, the superficial digital flexor tendon branches, the collateral ligaments, and the distal sesamoidean ligaments are all common factors. If these tissues are stretched or torn, and the joint is instabilized by the injury, new bone is produced to help to stabilize the joint. Osteoarthritis (the endstage of degenerative joint disease) of the pastern or coffin joint is a very common cause of articular ringbone. Bone is then produced to try to immobilize the joint and to relieve the chronic inflammation of the joint capsule. This process may take years, and lameness will continue until the joint is completely immobilized.
Trauma to the periosteum can cause bone growth on the pastern bone. However, this is usually not progressive unless nearby soft tissue was also harmed and thus the joint instability was affected.
Poor shoeing and conformation, such as long, sloping pasterns, upright pasterns, long-toes with low heels, pigeon toes, splay foot, or unbalanced feet may predispose the horse to ringbone, as they create uneven stress on the pastern and coffin joint, unequal tension on the soft tissues, or worsen the concussion that is absorbed by the pastern area.
Signs of Ringbone
Ringbone usually occurs in the front legs, and is usually worse in one leg than the other. Ringbone is most often found in mature horses, especially those in intensive training.
High ringbone: (Affects the Paster joint) The horse will have a bony growth around the pastern area, and the pastern will have less mobility. The horse will show pain when the pastern joint is moved or rotated. Early cases will have a lameness score of 1-2 out of 5, with little or no bony swelling seen, although possibly felt when compared to the opposite pastern. Lameness will worsen to a grade 2-3 on a scale of 5 as the ringbone worsens.
Low ringbone: (Affects the coffin joint) The horse will have moderate lameness (grade 2-3), even in early cases, because of the closeness of the ringbone to the other structures in the hoof. When severe or very advanced, the bony growth will be able to be seen on the coronet.
Prognosis for Ringbone
If the ringbone is close to a joint, the prognosis for the horse's continued athletic use is not as good as if the ringbone is not near a joint. Ringbone that is progressing rapidly has a poorer prognosis as well. Horses that are not performing strenuous work, such as jumping or working at speed, will probably be usable for years to come. However, horses competing in intense sports may not be able to continue at their previous level, as their pastern joints are constantly stressed.
If your horse does develop ringbone, which can occur as an animal ages--usually around 15 years of age--be sure to have him trimmed and shod on a regular basis to keep the foot in balance. Shoes that help his feet break over, such as those with a rolled toe, can minimize the torque on the pastern joint and reduce pain. Chondroprotective such as glucosamine and chondroitin agents have been shown to help. Maintain a healthy weight for your horse.
For More Information:Shoeing Prescription for Ringbone
Ringbone and Sidebone
Sources: King, Christine, BVSc, MACVSc, and Mansmann, Richard, VDM, PhD. 1997. "Equine Lameness." Equine Research, Inc. Pages 694-699.