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While many people tend to think of equine arthritis as a senior horse problem, the condition can affect horses of any age.
Sport horses are at higher risk of arthritis due to the nature and intensity of their work. It is estimated that up to 60% of all lameness in horses stems from arthritis or joint disease. [1]
Arthritis is defined as inflammation in one or more joints, which leads to pain and stiffness. The condition is degenerative, meaning it cannot be reversed in most cases and tends to worsen over time.
However, there are steps that horse owners can take to lessen symptoms and also slow the progression of the disease.
Detecting equine arthritis early and managing your horse appropriately are both keys to getting inflammation under control. In many cases, by the time a horse is lame, the arthritis is already advanced.
Managing arthritis relies on treatments that alleviate pain and reduce the progression of the disease. Anti-inflammatory pharmaceuticals and nutritional supplements can be beneficial for alleviating symptoms and improving mobility and quality of life.
Feeding programs that provide omega-3 fatty acids like EPA and DHA can also support joint health, improve comfort and help your horse return to soundness.
Submit your horse’s diet online for assessment by our equine nutritionists and for suggestions on supporting joint health and managing symptoms of arthritis.
Normal Joint Function in Horses
To understand how arthritis affects a horse, it is important to first understand the anatomy and function of healthy equine joints.
Joints are where two or more bones meet in the body, allowing for movement. Horses have three types of joints:
- Synovial joints: These types of joints include the knee, fetlock and hock. Cartilage covers the ends of the bones. The joints consist of a synovial cavity filled with lubricating and shock-absorbing synovial fluid between the bones.The synovial fluid is contained within the joint capsule. These joints allow for flexion, extension and rotation as with ball and socket joints.
- Fibrous joints: Less common than synovial joints, fibrous joints do not allow for movement between bones. An example would be the joints between bones in the horse’s skull.
- Cartilaginous joints: Occurring where bones are connected by cartilage, these joints allow limited movement and provide shock absorption. The joints between the vertebrae in the horse’s spine are an example of cartilaginous joints.
Arthritis can occur in both synovial and cartilaginous joints but it is most commonly diagnosed in the synovial joints of the leg.
Types of Arthritis in Horses
Three main forms of arthritis can occur in horses: osteoarthritis, traumatic arthritis, and septic arthritis.
All three forms have different root causes and can vary in severity. As a result, they may require different types of treatment.
Osteoarthritis (OA)
OA is the most common form of arthritis and cause of lameness in horses. This condition is also known as degenerative joint disease.
Osteoarthritis can be triggered by:
- Everyday wear and tear
- Repetitive motions; especially those involving excessive force
- Poor conformation
OA involves chronic, progressive, and painful degeneration of the articular cartilage, subchondral bone thickening (sclerosis), osteophytes (small bony growths), and synovial inflammation. [2]
It can affect any joint, but most commonly affects the hocks, knees, stifles, and fetlocks.
Traumatic Arthritis
Many horses develop arthritis in a joint after sustaining an injury in the area. Traumatic arthritis involves inflammation of the synovial membrane and joint capsule, leading to gradual loss of cartilage.
Also known as post-traumatic osteoarthritis (PTOA), the condition is often caused by fractures, articular cartilage lesions, ligament tears or ruptures, cartilage tears, or a combination of these injuries. [3]
Septic Arthritis
Septic arthritis differs from OA and PTOA in that it is caused by the penetration of microorganisms into the joint. It most often develops after intra-articular injections, wounds, or surgery, and commonly involves the hock joint. [4]
Septic arthritis tends to worsen rapidly, leading to extreme lameness. However, the severity of this condition is often linked with the horse’s age, immune status, and the type or amount of infective microorganisms.
Septic arthritis is a serious condition that warrants immediate veterinary attention. The survival rates tend to be lowest for foals but higher in adult horses. The prognosis for adult horses is influenced by the cause of the disease, duration of infection, presence of additional lesions, as well as the treatment protocol.
Studies show that horses treated aggressively during the first 24 hours after onset have the most positive outcome. However, septic arthritis also comes with possible complications such as laminitis, tendonitis, and osteoarthritis, which may limit the horse’s future career. [4]
Symptoms of Equine Arthritis
Horses in the very early stages of arthritis often don’t show symptoms. As the condition progresses, the most common symptoms include:
- Stiffness
- Pain, warmth, and swelling of joints
- Tenderness in affected limb
- Reluctance to exercise
- Back pain
- Slight edema (swelling) of lower leg
- Loss of appetite
- Gait abnormalities
Symptoms tend to worsen over time, especially if the condition is left untreated.
Diagnosing Arthritis in Horses
Diagnosing arthritis is not always easy, especially in the early stages when horses may not show symptoms or may only show very mild symptoms.
In fact, the inability to detect early changes has significantly hindered the development of effective therapies. [5]
A variety of imaging techniques, as well as synovial fluid analysis, can help veterinarians diagnose arthritis in horses. [6]
Radiography
This is the most commonly used diagnostic tool for detecting arthritis. X-rays can identify bone chips or bony growths in the joint.
X-rays can also identify narrowed spaces between joints, which are associated with a breakdown of articular cartilage.
However, radiography often does not show early changes in joints. It is more useful when the disease has progressed to a certain point.
Computed Tomography (CT Scan)
This diagnostic tool takes multiple X-ray images at different angles across the limb while the horse is anesthetized. It produces a series of “sliced” images which provide detailed pictures of the structure and shape of the bone.
CT also provides information on bone density which can be helpful in the diagnosis of arthritis.
Arthroscopy
This technique is more invasive than radiography or computed tomography, but is considered the gold standard for detecting changes in cartilage. [6]
Arthroscopy involves the insertion of a small endoscope into the joint, allowing a clear view inside that joint. It is also helpful for detecting joint capsule and intra-capsular lesions. [6]
Nuclear Scintigraphy (Bone Scan)
This diagnostic tool can be used to detect inflammation in joints. It involves using a radioactive dye that is injected into the horse’s bloodstream where it diffuses out of the blood vessels and concentrates in areas of inflammation.
The dye can then be viewed with a special camera.
Ultrasound
This tool is useful for evaluating damage to soft tissue in and around joints, including ligaments and tendons. It does not, however, show problems associated with bone or the joint itself.
Biomarkers
Biomarker analysis has been useful in early diagnosis of arthritis or joint disease. A biomarker is a substance that is measured and used to indicate the status of a metabolic process inside the horse’s body.
For example, biomarkers in synovial fluid and blood serum can be measured to detect changes in the joint. Levels of prostaglandin E2 (PGE2) in synovial fluid indicate the amount of inflammation in the joint. [7]
Treatment of Equine Arthritis
Because arthritis cannot be reversed in most cases, the primary goal of treatment is to reduce inflammation and manage pain to make your horse more comfortable.
In horses with early osteoarthritis, therapeutic strategies aim to preserve tissue structure and function to prevent further damage. [2]
The most commonly used treatments for equine arthritis include corticosteroids, nutraceuticals, non-steroidal anti-inflammatory drugs (NSAIDs), and joint injections.
Oral medications are easy to administer and often effective at managing pain. However, long-term use of corticosteroids or NSAIDs can result in side effects. Several advanced technologies show promise for treating osteoarthritis.
For septic arthritis, treatment involves targeting the infective microorganisms. Antibiotics are often given for two to four weeks. Lavage of the infected joint is also commonly performed by veterinarians. [8]
NSAIDs
Non-steroidal anti-inflammatories drugs, such as phenylbutazone (bute), have long been used to manage pain associated with equine arthritis.
This class of drugs is effective for controlling short-term flare-ups, but negative side effects can occur with long-term use. Traditional NSAIDs alone are not an ideal solution for long-term management of equine arthritis.
A newer type of selective NSAID, firocoxib (Equioxx), works differently from traditional NSAIDs by blocking COX-2 enzymes instead of COX-1. Firocoxib is associated with fewer side effects and is less irritating on the gastrointestinal tract.
Studies have shown that firocoxib is as effective as bute in reducing lameness associated with arthritis and may lead to greater improvement in range of motion. [7] Because of this, firocoxib may be a better option for long-term pain management associated with OA.
Topical NSAIDs are another alternative to traditional NSAIDs. Diclofenac sodium (Surpass) can be applied directly to affected joints. This medication has low systemic absorption, which means there are fewer potential gastrointestinal side effects compared to oral NSAIDs like bute.
Intra-Articular Injections
Intra-articular injections are administered directly into the joint by a veterinarian. They contain hyaluronic acid, polysulfated glycosaminoglycans, or corticosteroids.
This is a commonly used treatment for arthritis, but horse owners should be aware that this type of injection carries some risk. Adverse reactions can include joint inflammation, infection, and septic arthritis.
Regenerative Medicine
Certain naturally occurring products taken from the horse’s body can also be injected into the joint. Regenerative medicine has the potential to prevent further cartilage damage and possibly reverse the damage.
The following are all forms of regenerative medicine used to treat joint disease in horses:
- Autologous Conditioned Serum (ACS) is the liquid portion extracted from the horse’s own blood and processed to increase concentration ofcytokines and growth factors. ACS is a source of beneficial anti-inflammatory mediators, most notably interleukin-1 receptor antagonist protein (IRAP). Clinical studies report improved synovial membrane health, stimulation of natural IRAP production, and improvements in lameness scores in horses treated with ACS. [9]
- Platelet—Rich Plasma (PRP) is blood plasma that is filtrated to contain a higher concentration of platelets than whole blood. Used in tendon and ligament injuries as well, PRP is regularly administered to treat joint disease. [10]
- Autologous Protein Solution (APS) Marketed under the name Pro-Stride, this product combines the technology of both ACS and PRP. The horse’s own blood is used to make a solution rich in white blood cells, platelets, and serum proteins that are injected into the joint. One study indicated that intra-articular injection of APS significantly improved lameness and joint range of motion in horses with mild joint disease. [11]
- Mesenchymal Stem Cells (MSCs) are adult stem cells derived from fat or bone marrow. Stem cell treatment has been used in soft tissue injuries for some time to regenerate and repair damaged tissue.
Recently, veterinarians have begun using stem cells to treat equine arthritis with some encouraging preliminary data. More research is needed to understand whether MSCs will match the success of other forms of regenerative medicine in treating equine osteoarthritis. [12]
Extracorporeal Shockwave Therapy (ESWT)
This treatment involves directing energy waves at a specific site on the horse’s body. One study showed that ESWT treatment improved lameness and indicators of joint disease. [13]
However, more research is needed to assess the effectiveness of this treatment compared to other common treatment options.
Surgery
For severe cases of arthritis in which there is no other way to alleviate a horse’s pain, fusing a joint via chemical, laser, or physical surgery can help.
With the source of friction removed, pain is diminished and some horses may even be sound enough for riding. [14]
Nutritional Support of Joint Health
A number of oral nutraceuticals are supplemented to support equine joint health.
The most popular ingredients for equine joint health include glucosamine and chondroitin sulphate.
These are substances found naturally in joints that help to repair cartilage and ease inflammation. However, their effectiveness as oral supplements has not been adequately demonstrated in research trials involving horses. [15]
Other supplement ingredients, such as MSM, hyaluronic acid and DHA, are supported by research. Some newer supplements contain soybean and avocado unsaponifiables (ASU) which may reduce inflammation and protect cartilage. [16]
Vitamin and Mineral Supplementation
Like all tissues in the horse’s body, healthy joints rely on adequate nutrition to support tissue growth and maintenance.
Nutrient deficiencies can impair metabolic processes and enzyme systems that are required for joint function and repair. Key vitamins and minerals for joint health include:
- Zinc and copper: These trace minerals affect cartilage remodelling; deficiencies can affect joint health in growing horses [17]
- Manganese: This trace mineral is an important co-factor for enzymes that synthesize glycosaminoglycans (GAGs) such as chondroitin sulfate and hyaluronan [14]
- Selenium, Vitamin E & Vitamin C: These are antioxidants that act throughout the body to neutralize free radicals produced during normal metabolic processes. Antioxidants limit oxidative damage in tissues, including joints
- Sulfur: This macromineral is an important component of glucosamine and collagen, helping to maintain healthy connective tissue and cartilage.Supplementation with the natural compound MSM (methylsulfonylmethane) provides a highly bioavailable form of sulfur to support joint health