In this post, we are going to examine a few interesting and important aspects of the equine skeletal system. We will look at bone growth, how to properly train the skeletal system, and common problems that can occur.
How Equine Bones Grow
Equine bones grow in two different ways: longitudinally and in circumference. Longitudinal bone growth occurs at both ends of the bone to increase length.
Essentially, cartilage is laid down by growth plates and then ossified to form bone. The shaft (diaphysis) is pushed away from the head (epiphysis), thereby increasing the length of the bone. Once the bone reaches maturity, the growth plate is ossified and closes.
It is important to note that bones mature at different times and more distal bones mature prior to the more proximal bones. In simpler terms, bones that are farther away from the body (coffin bone, cannon bone, etc.) mature faster than bones that are closer to the body (vertebrae, pelvis, etc.).
Bone (re)modeling refers to the growth that occurs around the shaft of the bone to alter size and shape (circumference). In this process, osteoblasts add bone and osteoclasts take bone away.
During this process, the bone is put in a vulnerable state. The purpose of bone remodeling is for bone repair, adaptation, and calcium homeostasis.
So, why is it important to understand these processes? Well, riding prior to allowing the growth plates to fuse can cause structural damage to the back and legs of the horse. This may also teach the horse to protect themselves from the pain and discourage them from rounding their back and collecting during riding.
How To Properly Train the Equine Skeletal System
There are many things you can do to help lessen the stress put on the equine skeletal system.
First and foremost, proper turn-out is KEY. Horses are meant to move around and use their muscles and bones. If they are kept inside and aren’t able to move around freely, they can be more prone to skeletal and muscular injury and will have a harder time maintaining their physical condition.
Second, short periods of high-impact training are found to be sufficient enough to bring about increased bone mass. This is desired as thicker bones are stronger and can be less prone to injury. A good example of this type of exercise would be 10 minutes of trotting on a firm surface.
Third, do not overload your horse. Excess fat on the horse, too large of a rider, or excessive riding when the horse is too young (under 4 years) are all detrimental to the equine skeletal system. Make sure to keep your horse in good physical condition and your riders proportional.
Fourth, be sure to train the horse on multiple surfaces and terrain you may see in your discipline’s competition – this allows them to adapt and have the proper training response desired.
Finally, step up the training load (intensity or duration) no more than once every 2 weeks. Rushing horses can easily lead to injury and early retirement.
Common Equine Bone Issues
Bucked Shins
Definition: painful, acute inflammation of the periosteum located on the dorsal surface of the cannon bone and often observed in young racehorses.
Cause: excessive compression on a bone that has not remodeled enough to tolerate the stress placed on it. The stressed bone forms a new layer of bone at the point of stress. This new bone is weaker and, due to the process of rapid bone formation, the periosteum becomes elevated and inflamed.
Treatment: short period of rest followed by a gradual increase in exercise to provide time for the bone to heal. Complete rest is not recommended as it can cause all new bone growth to be reabsorbed.
Ringbone
Definition: a painful condition characterized by new bone growth that affects either the pastern or coffin joint. It can also only impact the side of the pastern bone and be cosmetic if it fails to reach the joint.
Cause: Horses are predisposed to ringbone if they have upright pasterns or toed in conformation. Horses that undergo repetitive stress in the pastern region (jumpers, barrel horses, and polo ponies) are also at risk along with horses who suffer acute trauma to the pastern region.
Treatment: ringbone is an irreversible and progressive condition, manageable by keeping the horse at an ideal weight, adjusting trimming to reduce joint stress, joint injections, or intra-articular steroid injections.
Thank you so much for reading about the equine skeletal system. Let me know if any of the information in this post surprised you! I’d love to hear from you.
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References and bonus resources
Kentucky Equine Research – Principles of Bone Development in Horses
Iron Gate Equine Clinic – Ringbone in Horses – Diagnosis and Treatment