Equine Traumatic and Degenerative Joint Disease
By D. Craig Barnett, DVM
Introduction: There are many causes of lameness in the horse. However, traumatic joint disease is the most frequent cause of lameness in the equine athlete and the single biggest develops after single or repeated episodes of trauma, which occurs due to everyday use and imposed stress on the joint resulting in inflammation of the joint. The joint is composed of articular cartilage and soft tissue structures, which encase the joint. Soft tissue structures include the membrane lining the joint (the synovial membrane), the joint capsule and collateral ligaments. Inside the joint is joint fluid (synovial fluid). Trauma to the joint results in varying degrees of inflammation. In the early stages of traumatic joint disease the inflammation generally affects only the synovial membrane and joint capsule, but left untreated, it will usually progress to affect both the synovial membrane and the cartilage. Cartilage damage results in degenerative joint disease (DJD or osteroarthritis). Cartilage has a very limited ability to regenerate and heal. Therefore, (DJD) is not reversible and is a major cause of crippling lameness in the horse.
How does traumatic joint disease begin and progress? Traumatic joint disease begins with either a single episode of moderate to severe trauma to the joint, or, more commonly from repeated trauma or stress to the joint incurred during everyday use, athletic training, or performance. Repeated trauma to the joint may be initiated or exacerbated due to stress imposed on the joints from improper or inadequate hoof care. Correct and timely trimming/shoeing, which establishes a normal hoof/pastern axis and balance, is very critical to limiting stress on the joints, tendons and ligaments. Proper trimming/shoeing is important for limiting stress on the joints, and is even more important in the performance horse who already has elevated level of stress being imposed on the joints.
During the initial/early stages of traumatic joint disease, the inflammation usually only involves the soft tissue structure of the joint (the synovial membrane). At this stage, cartilage damage is usually spared. However, left untreated or allowed to continuously reoccur, the inflamed joint will produce enzymes (products of inflammation), which will usually degrade or damage the cartilage. Cartilage damage is the hallmark of degenerative joint disease (DJD). Degenerative joint disease can present in varying degrees from mild cartilage damage to more severe, extensive cartilage damage. Generally the more severe the cartilage damage, the worse the prognosis for being able to manage the associated lameness. Remember, cartilage has a very limited ability to regenerate and heal.
How do I know if my horse is experiencing traumatic joint disease or degenerative joint disease (osteoarthritis)? The earliest symptoms of equine traumatic joint disease related to the soft tissue inflammation (inflammation of the synovial membrane). At this stage, lameness may or may not be present. Early warning signs may include, but are not limited to, changes in performance such as reluctance to change leads, turn barrels, take jumps, etc. Although these problems may be related to behavior or training, the possibility of early joint sisease should not be overlooked. Other early signs of joint disease may include heat or swelling of the joint, painful response to joint flexion test, joint fluid distention/swelling (effusion), and varying degrees of lameness. The degree of lameness may range from a subtle lameness, only detected by an experienced observer, to a more noticeable, obvious lameness. A thorough examination by a veterinarian will help determine whether or not joint disease should be a concern. The examination will generally include observation and evaluation of the horse traveling at different gaits, hoof tester evaluation, palpation and manipulation of tendons and ligaments, and possibly nerve and/or joint blocks. Depending on the individual case, other diagnostic tests such as radiographs (x-rays), ultrasound examination, nuclear scintigraphy, CT/MRI scans, and arthroscopy may be indicated. Signs of more acute/early cases of traumatic joint disease often include heat, pain, and joint fluid distention with minimal or no radiographic changes. Moderate cases of traumatic joint disease usually have these signs of early joint disease plus a moderate amount of cartilage damage evident on radiographs or arthroscopy. More advanced cases of DJD will show signs indicative of significant cartilage damage.
What are my treatment options if my horse is diagnosed with traumatice or degenerative joint disease? Once a diagnosis of traumatic joint disease is made, treatment will depend upon the severity and stage (acute vs chronic) of the disease, underlying causes or exacerbating conditions such as unbalanced feet or improper hoof/pastern axis, the individual veterinarians experience with different treatments, and the individual expectations of the horse. Early stages of traumatic joint disease (before cartilage damage has taken place), usually respond better to treatment. Therefore, the therapeutic goal is to treat traumatic joint disease as early as possible. Treatment should be aimed at addressing any underlying problems such as improper hoof/pastern axis or unbalanced feet to help relieve the stress and strain this may be having on the joint. Teamwork between veterinarians and farriers is very important in helping to treat and manage many joint disease problems. Treatment is aimed at relieving soft tissue inflammation and pain, restoring the joint and joint fluid to a pre-injury state, and preventing secondary cartilage damage. Along with proper trimming/shoeing, most horses will require additional therapy. Other treatments include rest, physical therapy, nonsteroidal anti-inflammatory drugs (NSAIDs) such as phenlybutazone or Banamine, sodium hyaluronate (HA) such as Legend, polysulfated glycosaminoglycam (Adequan), corticosteroids, and oral chondroprotectie agents. Before proper therapy can be administered, it is imperative that the horse be examined and a diagnosis made. Each horse must be evaluated individually and treatment must be tailored towards that particular condition. The clinicians' choice of therapy is usually based on the individual case, the clinicians' experience with different drugs, and the individual performance requirements of the horse.
