Understanding the causes and diagnosis of arthritis.
Arthritis is a diagnosis no horse owner wants to hear. It conjures up negative images of lifelong lameness, stiffness and pain. In the first part of this article, we will look at the definition of arthritis, its causes, and how it’s diagnosed. In the next issue, we will cover prevention and treatment options, including both conventional and complementary/alternative measures.
What is Arthritis?
Osteoarthritis is a group of joint disorders. Left untreated, the end result is degradation/deterioration of the articular cartilage. This is often accompanied by negative changes in the soft tissue surrounding the joint, and in the bone within and on the edges of the joint. In either case, the sign we observe is lameness. This lameness may be present all the time, or only in certain situations. In acute joint damage, there is often some swelling of the tissue around the joint. In chronic cases, there may actually be palpable bony enlargement around the joint.
Arthritis can be loosely divided into two traditional categories, although there is some overlap between them.
1. The first is an acute condition, the result of a traumatic or performance injury. It is commonly associated with acute swelling of the synovial membrane (synovitis) and usually occurs in high motion joints – i.e. the carpus (commonly referred to as the knee), upper tarsus (hock), or the stifle.
2. The second category is a more insidious disease and typically presents in low motion joints – i.e. pastern and coffin joints in the front and hind limbs, and the lower tarsal joints. We usually see this type in older horses, or those subjected to repetitive motion in their training.
Two Types of Arthritis
Synovitis (inflammation of the synovial membrane) can occur with an acute injury to a joint. It could be a strain or sprain and may be caused by a fall, landing “wrong” after a jump, or any other number of pasture or ridden injuries. The owner will most often observe swelling in and around the joint, and the horse will be lame. If extensive enough and left untreated, synovitis can lead to deterioration of the cartilage that lines the joint surfaces. This is because injured synovial cells produce substances that are toxic to the cartilage. In this acute phase, treatment should be focused on decreasing inflammation in the joint.
Repetitive motion injury is a more insidious form of arthritis, and is caused by repetitive motion in low motion joints. This is more of a chronic use disease, and is often associated with horses that have had the same job their whole lives. This form of arthritis is also seen in horses that have an uncorrected angular limb deformity. Abnormal limb angulation or poor conformation can place abnormal stresses on the joints in both the affected limb, and the rest of the horse as he compensates for the abnormal limb structure.
The Unstable Joint
If we look at these two forms of arthritis from a more holistic point of view, the picture is slightly different and each form has essentially the same cause. Osteoarthritis is caused by a chronically unstable joint. This instability can be so slight it often goes unnoticed by the owner/rider/trainer. Horses are designed to function optimally, but are masters at hiding decreased function. This is a necessary defense mechanism that developed so horses in the wild could stay alive. Optimal function dictates that all joints work perfectly to keep the horse moving efficiently. When the muscles and tendons that cross and support a joint are not functioning optimally, then the joint is less stable. This instability can cause a normal activity to become an acute trauma – i.e. landing after a jump, causing synovitis, or a normal activity repeated time and again to cause repetitive motion injury.
The diagnosis of osteoarthritis can be difficult, time consuming, and expensive. The first step is to isolate the lameness to a certain joint or joints. If the horse suffered an acute injury and a joint is swollen, this is an easy step! If not, a lameness exam will be performed.
A thorough exam will start with obtaining a complete history, followed by palpating the horse’s limbs and watching him move. Depending on the degree of lameness, and when the owner/rider notices it, the veterinarian may watch the horse work on a lunge line, in a straight line, and/or under saddle (or hitched to a cart if this is applicable). The veterinarian may flex each of the horse’s limbs and watch him trot after the limbs are flexed. This “flexion test”, while not diagnostic, can help point the veterinarian in the right direction.
Once it is determined what limb the pain seems to be originating from, the veterinarian will try to isolate the exact area. This is often done with sequential nerve blocks. An anesthetic agent is used to numb the nerves, starting with those that innervate the heels and working up. After the nerves are numb, the horse will again be asked to move as before. The blocking will continue until the lameness is at least 80% resolved. At this point, the area causing pain is located between the last two areas that were anesthetized, and imaging of the area can begin.
There are different techniques we can use to image the body. The most widely known are radiographs (commonly and incorrectly known as x-rays) and ultrasound.
• Radiographs are used to image bone. They are utilized to rule out fractures and recognize bony changes in and around joints due to chronic osteoarthritis.
• Ultrasound is used to look at the soft tissue around and within joints. It is as much art as science, and needs to be performed by someone with experience in musculoskeletal ultrasound.
If the area of lameness has been isolated and no abnormalities show up on radiographs and ultrasound, further diagnostics are warranted. Most often, acute joint damage will not show up on radiographs and ultrasound. In order to visualize the damage, the veterinarian may recommend CT (computed tomography) or MRI, which utilize different technologies to produce images. Arthroscopy may also be used; a sterile camera probe is inserted into the joint, allowing the veterinarian to visualize its interior in real time. All these imaging techniques require general anesthesia (there are standing MRI units that only require light sedation). They are considered advanced techniques and are available at large referral clinics and veterinary teaching hospitals.
Once a diagnosis is made, treatment can begin. In the second half of this article, we will cover alternative and conventional treatments, and methods for preventing arthritis.
Dr. Jennifer Miller owns Prairie Rivers Holistic Veterinary Service in Byron, Georgia. After practicing conventional equine veterinary medicine for a number of years she came to realize it did not offer all the answers to her patients’ needs. She obtained certification in Veterinary Spinal Manipulation Therapy from the Healing Oasis Wellness Center and in Veterinary Acupuncture from the Chi Institute. She has also studied Applied Kinesiology and Craniosacral Therapy. Dr. Jennifer is herself a student of the horse and studies classical dressage, lessoning as often as she can. She has a passion for functional neurology and loves being able to integrate functional neurology concepts with classical dressage. She lectures to groups on how understanding the neurology of the horse can make all of us more empathetic riders. PrairieRiversHolistics.com