Everything you need to know about horse joints

Their joints are key to a horses ability to be mobile and agile. When horse joints are healthy they provide a seamless system that allows them to move with ease and they will be sound. However they can and do become damaged often leading to significant claims on horse health insurance policies. The most common form of joint disease is osteoarthritis also known as degenerative joint disease DJD. In horses I have seen and treated osteoarthritis is normally the result of wear and tear in the joint over several years. I see it more commonly is middleaged to older horses but it can be found in younger performance horses too.

When your horse works small amounts of damage that occurs in the normal course of the joint functioning are repaired and the joint returns to normal. Eventually though damage may occur thats beyond the joints ability to repair. This results in inflammation and an increase in the breaking down processes within the horses joint at the expense of the building up for reparative processes.
When the damage exceeds a certain point cytokines are released by cells within the joint which in turn leads to further inflammation. As the joint becomes more inflamed the synovial membrane reacts by increasing synovial fluid production causing the joint to become swollen. As the amount of this fluid increases the quality of the fluid decreases. By this I mean it becomes thinner and has less shockabsorbing and lubricating ability resulting in further cartilage damage and worsening inflammation in the horses joint.
Types of joints
Each joint is made up of a group of components that work effectively together so that the horse can reach their full athletic potential. Horses have three types of joints cartilaginous fibrous and synovial.
Cartilaginous horse joints are connected by cartilage and have limited movement for example between the vertebrae in the spine.
Fibrous horse joints do not move at all like those that connect bones in the skull.
Synovial joints move the most and are usually whats being referred to when equestrians talk about joints. The fetlock knee and stifle are synovial joints
Inflammation of a horse joint
The presence of cytokines and of increased synovial fluid is detected by different receptors in the joint triggering pain signals and resulting in clinical lameness of the horse. If the joint remains inflamed then further changes may occur including
Thinning of the cartilage reducing its ability to protect the underlying bone.
Thickening and stiffness