The stability of a joint is important in the biomechanical function and soundness of our equine patients. When we talk about joint stability, people will think that we are talking about wrapping a lower leg for tendon or fetlock support. But actually we were talking about the stability of all joints in the body. Joints are stabilized by numerous structures, including the joint capsule, ligaments, the shape of the joint and muscles or the muscle unit as the tendon crosses the joint. We will discuss these structures in more detail, but first I want to discuss why joint stability is important.
When a joint lacks stability, pathology or disease develops in the joint. The lack of stability is called laxity or play in the joint. When we have laxity in the joint, the joint undergoes micro-trauma. Micro trauma initiates a destructive process in the joint. This destructive process is started with an inflammatory reaction, also known as synovitis. The inflammatory enzymes cause destruction of the joint capsule, cartilage, and the integrity of the joint fluid. This process is called arthritis(link) and leads to degenerative joint disease or DJD(link).
The joint undergoes a process to try to secure the joint. The micro-trauma initiated inflamed joint creates distention in the joint capsule which helps to stabilize the joint. We do not like this method of stabilization since inflammatory enzymes destroy the integrity of the joint fluid and joint structures. But it is the body‘s way to try to stabilize the joint. With this inflammation and heat along with the swelling, the body uses the joint less which will help decrease the destruction of the joint structures.
In Traditional Veterinary Medicine this is a joint that would be injected with a steroid or joint fluid enhancing product or cartilage protecting product(link). These are products used to try to reduce the inflammation and the destruction caused by the inflammation. But in Integrative Veterinary Medicine(link) we stabilize the joints reducing the micro-trauma and stopping the inflammatory process from occurring.
Let’s return to the stabilizing structures of the joint, the joint capsule and shape of the joint contribute a small percentage to the stability of the joint. The ligaments of the joint especially the collateral ligaments of the joint which are the pivot points for the joint contribute up to about 17% of the joint’s stability. But the muscle unit(link) or the muscle itself creates the highest percentage of stability for the joint. The muscle unit provides about 80% of the joint’s stability. A muscle unit consists of the muscle, the tendon and the insertion attachments to the bone.
Muscle function or strength is determined by two mechanisms, one the concentration or number of muscle myofibrils, second the amount of nerve impulse to stimulate the muscle. The concentration or number of muscle muscle myofibrils is the amount of muscle contracting proteins that is contained in a muscle(link). This can be increased by exercise and proper nutrition. But what is more important to muscle contractibility or strength is how much of the muscle is stimulated by the nerve impulse. If the nerve impulse to the muscle is decreased the amount of the muscle activated for contraction is also decreased. Therefore a week muscle scenario is created.
A weak muscles scenario can be corrected with a Chiropractic manipulation. When we have a reduced motion of the vertebral joints, the nerve function is decreased(link). By adjusting the vertebrae and increasing the motion in the vertebral joints, the nerve function is restored. Normal nerve function to the muscle will return the muscle to proper strength level. Another component of a weak muscles scenario is a Central Pattern Generator deficit(link). Each Central Pattern Generator(CPG)has an indicator muscle that is weak when a deficit occurs with the CPG. Since muscles provide 80% of the stability to all joints, whichever joint the weak indicator muscle stabilizes, the joint will have laxity resulting in micro-trauma.
As illustrated, joint stability or the lack there of is important in the health of our equine patients. The joint instability creating the inflamed or arthritic joint can be treated in two fashions. One method assists in reduction of joint inflammation by injections and covering over the problem. Or the joint instability can be corrected by returning the joint stability to normal with improved muscle function. Improving the muscles capability to stabilize the joint solves the problem of joint instability. The method of solving this joint instability problem is provided with Integrative Veterinary Medicine which includes Applied Kinesiology and Chiropractic manipulation.