Ringbone and Arthritis

A common problem to see in our equine patients is what is termed ringbone. Many may be familiar with this term, but unfamiliar with exactly what it is. Ringbone is essentially arthritis formation in pastern region of the front or rear limbs of the horse. To be even more technical, the ringbone is defined as either "high" or "low". High ringbone is arthritis associated with the pastern joint while low ringbone is associated with the coffin joint. Even further, it is delineated as either intra-articular (involving the joint) on non-articular (not involving the joint). Intra-articular ringbone leads to more pain development due to being involved with movement. In many cases, we will clinically diagnose non-articular ringbone in a clinically sound patient, which in most cases is more a cosmetic deformity or swelling in the pastern region. There are many causes for ringbone formation, which are: conformation, genetics, foot balance as well as injury to the region due to excessive use. I would like to demonstrate a few factors in a case involving a patient seen at our clinic. This is a 15 year old warmblood gelding that had a jumping career for the majority of his life.

This is the x-ray image of the RF digital region of the warmblood. Here we can see several things. First, we need to look at overall conformation or alignment of the phalangeal bones, which are P1, P2 and P3. P1 is the bone directly below the fetlock joint, P2 is the middle bone and P3 is the coffin bone which is held inside the hoof capsule. In ideal cases, all three of these bones are in alignment with each other at an angle, which is shown by the red line. As you can see, the bones don't correspond to this line, but essentially have a concave type of architecture in their alignment. This type of alignment leads to increased stress on the joint, which then contributes to joint damage. The arrow in the photo helps to point out the new bone formation or arthritis that has developed in the coffin joint and surrounding area. In this case, the ringbone is intra-articular as well as extra or non-articular.

Here is the x-ray image of the left front digital region. Again, here we have a red line which indicates more or less what the alignment of the three phalangeal bones should be. As you can see, in comparison to the other x-ray, in this foot, the bones are more closely in alignment with one another. However, there is rotation of the coffin bone, which is indicative of laminitis in the chronic sense. The white arrow indicates intra-articular ringbone formation in the coffin joint as well, but to a lower degree than in the left front foot. So, the question comes as to how to treat this patient and reduce his pain levels. In this particular case, we have opted to change the angles of his feet by trimming to help align the bones and change the angle of P3. One has to be careful in terms of trimming and changing angles because many of these guys have adapted to their current angles and the arthritis has somewhat "fused" the joint in that position. The pain that these horses feel comes from not only poor angles but also movement of the arthritis or boney spurs as he moves. In most cases, once the arthritis has bridged the joint and fused, the pain is reduced dramatically. The hard part comes in getting that joint to fuse. That is another story. Aside from trimming, he is being managed on low dose bute therapy once daily in conjunction with a special custom blend of our Cur-OST EQ Green product. He is also receiving initial doses of Adequan to aid in overall joint health. When he presented initially, he was a grade 4/5 in terms of lameness but within one week, he was more comfortable at a grade 2/5. I hope this helps to improve the understanding of ringbone in horses. Best, Tom Schell, D.V.M.