By Diane Gibbard

It is estimated that a staggering 60 percent of all equine lameness is due to arthritis and joint disease. One of the biggest challenges is that some arthritic horses might not show signs of lameness when there is damage and inflammation in the joint; therefore, proper prevention and early diagnosis is key to managing the progression of joint disease.

There are many potential causes of equine arthritis.

The everyday wear-and-tear of repetitive and excessive force on a joint may wear down the supporting tissues. Weightbearing joints, including the knee, hock, fetlock, pastern, and coffin joints are more prone to be arthritic since they endure the majority of the concussive forces. Poor conformation may exacerbate this, placing additional strain on joints.

A physical injury can trigger inflammation, and other types of injuries, such as a bacterial infection (septic arthritis) or a joint fracture, will stimulate an inflammatory response.

Everyday wear-and-tear and the cumulative stress of repetitive activities may wear down the joint’s supporting tissues. Photo: Shutterstock/PROMA1

Weightbearing joints that sustain the majority of concussive forces are more prone to arthritis and joint disease. Conformation abnormalities can worsen the effect. Photo: Canstock/Kapai

PREVENTION - WHAT CAN YOU DO?

Learn about basic joint anatomy and spot problems early by checking the horse’s legs for pain, swelling, heat, and new lumps, using the opposite limb for comparison. Photo: iStock/AnnaElizabethPhotography

Look for pain, swelling, heat, and loss of function. Signs of pain such as lameness or soreness upon palpation of the joint may indicate inflammation in a joint.

Swelling: Acute swelling (sudden onset) occurs as a result of blood vessel dilation and the movement of fluid into the joint to help repair damaged tissues. This type of swelling is often soft to touch and the horse may be sore upon palpation. Chronic swelling, or long term swelling, of an inflamed joint may feel harder due to the production of new bone as a result of the chronic inflammatory process.

Heat: When a joint becomes inflamed, the temperature might rise as much as one degree Celsius above resting body temperature, which can be useful as a diagnostic tool given the appropriate equipment (our hands are likely not sensitive enough to notice this small change in temperature).

Visual Exam: Inflammation in the joint might be visible from the outside due to swelling. Noticing and identifying any swelling at an early stage might help in the early diagnosis of joint disease.

Palpation: Palpating, or feeling, your horse’s joint is an easy method to identify potential inflammation. Familiarize yourself with basic joint anatomy and know what is normal, and which lumps should and shouldn’t be there. You may also use the opposite leg of your horse for comparison. When you are feeling your horse’s leg, check for any signs of heat, swelling, pain, and reduced range of motion.

If you suspect any signs of inflammation, speak to your vet. Veterinarians have a wide range of diagnostic tools at their disposal.

Related: The Healthy Senior Horse

DIAGNOSIS - WHAT CAN YOUR VETERINARIAN DO?

The most commonly used diagnostic tool to help pinpoint joint-related lameness is the X-ray. Photo: Shutterstock/Osetrik

It is important to work closely with your veterinarian to properly diagnose and design an appropriate treatment program for your horse. Here are a few diagnostic tools that vets use to help in the diagnosis of joint disease.

During a clinical examination, your vet might perform any number of tests including flexion test and nerve blocks (anesthetic blocks) to help pinpoint any joint-related lameness. Other tools described below are used alone or in conjunction to help in the diagnosis of the joint disease.

Joint Imaging Techniques

X‐Rays (Bone): X‐ray is the most commonly used diagnostic tool in joint disease. It is often used as the first stage of diagnosis given its practicality and ease of use. X‐rays are able to identify the presence of bone chips and the growth of new bone that is associated with certain cases of osteoarthritis. Narrowing of the space between the bones in a joint, which is associated with the breakdown of articular cartilage, can also be seen in an X‐ray; however, this is only seen in later stages of joint disease. Unfortunately, X‐rays are not able to show changes in articular cartilage since it is mostly made up of water and doesn’t show up on an X‐ray.

Computed Tomography – CT (Bone): A CT scan takes multiple X‐ray images at different angles across the limb while the horse is anesthetized. A computer then produces a series of “sliced” images. This allows for very detailed pictures of the structure and shape of the bone as well its bone density, which can be very helpful in the diagnosis of joint disease.

Arthroscopy (Cartilage): Diagnostic arthroscopy is a new technique that is currently being researched. It is more invasive that traditional techniques as it involves the insertion of a small endoscope into the joint and distending the joint with fluid, which allows for a clear view of the inside of the joint. Unlike the X‐ray, this technique is more sensitive and allows defects in joint cartilage to be seen.

Nuclear Scintigraphy – Bone Scan (Inflammation): A bone scan is able to detect inflammation in the joint. During inflammation, there is an increase in the dilation of blood vessels in the joint, which can be detected using a bone scan. In this test, a radioactive dye is injected into the bloodstream of the horse, and the dye diffuses out of the blood vessels and concentrates in an area of inflammation, which can be seen with a special camera. Although this technique is very sensitive, it is not specific to the problem causing the inflammation.

Ultrasound (Soft Tissue): An ultrasound is useful to evaluate any damage to soft tissue in and around the joints including ligaments and tendons. It does not indicate problems associated with bone disorder and/or inflammation in the joint.

Biological Techniques

Serum biomarkers (Early detection of changes in bone and cartilage): Serum biomarkers have been shown to be very useful in early diagnosis of joint disease. A biomarker is a substance/element that is measured and used to indicate the status of a metabolic process inside the horse’s body. Biomarkers inside the synovial fluid and blood serum can be measured to detect changes in the joint. For example, when articular cartilage is degraded, there is a breakdown of collagen and the subsequent release of molecules and enzymes (such as proteoglycans) can be detected in blood or synovial samples. An increase in these enzymes measured in the blood might indicate joint disease.

Related: Imaging for Horses: A Closer Look

TREATMENTS

Veterinarians can inject medication directly into the joint to control inflammation. Photo: iStock/Groomee

The primary goal in the treatment of joint disease is to reduce inflammation in the joint. It is critical to prevent the products of inflammation, such as interleukin (IL‐1), from further damaging the joint — specifically the articular cartilage. Pain relief is also an important factor when looking at the treatment of joint inflammation and arthritis as this is a very debilitating and painful disease.

Nonsteroidal Anti‐inflammatory Drugs (NSAIDs): NSAID’s are anti-inflammatory agents that inhibit some of the enzymes involved in the inflammatory process that cause damage to the synovial fluid, collagen matrix, and articular cartilage. Although NSAID’s have been shown to help manage joint inflammation, care needs to be taken when using NSAID’s since negative side effects might occur.

Intra‐Articular Injection: Joint injections allow veterinarians to administer medications directly into the joint. The most common medications administered are corticosteroids, hyaluronic agents, and polysulfated glycosaminoglycans (PSGAG). All these medications are used to control the process of inflammation through different metabolic pathways. Other products derived from the horse’s own body can also be injected into the joint — these include interleukin receptor antagonist protein (IRAP), stem cells and platelet rich plasma (PRP). Research on these techniques is ongoing.

Related: Equine Symptomatic Lameness

Published with the kind permission of Equine Guelph.

ABOVE: A joint is where two bones meet. A normal joint allows for proper movement and it needs a good framework of bone, cartilage, synovial fluid, ligaments, tendons, and muscles to function properly.

ABOVE: When injury occurs, inflammation may result. Inflammation is a normal and protective response to an injury, and signs include heat, pain, swelling, and loss of function. Normal inflammation helps repair injured tissue by dilating blood vessels, releasing white blood cells and enzymes into the joint to “mop up” damaged tissue. Unfortunately, sometimes these enzymes go out of control and will break down synovial fluid (joint lubrication) and proteoglycans (which hold the integrity of the collagen). This in turn stimulates further inflammation. Controlling inflammation is key to stopping this vicious cycle and preventing further damage to the joint.

ABOVE: After a phase of acute inflammation, a joint may return to normal. This is the best-case scenario.

ABOVE: In cases where inflammation is chronic, it progresses slowly and is often uncontrolled. This can lead to the breakdown of cartilage within a joint. Here, the degradation of articular cartilage by the inflammatory molecules outweighs its capacity to synthesize a new layer. This can eventually lead to osteoarthritis and degenerative joint disease. This results in reduced and damaged cartilage, and a scenario in which bones are virtually rubbing against each other.

LANGUAGE OF JOINT FUNCTION

Articular cartilage: Specialized tissue lining the ends of bones in a joint. It is composed of a matrix of collagen, proteoglycans (hyaluronic acid and chondroitin sulfate) and water. It allows for a smooth, gliding surface during joint movement and also acts as a shock absorber. Articular cartilage is continuously being remodeled by breaking down the matrix and replacing it with a new layer.

Bone: Serves as the framework for the horse’s body, where muscles, ligaments, and tendon attach. The bone in a joint supports all of the joint’s tissues, and joints need healthy bone to function properly.

Ligaments, tendons and muscles: All three are involved in providing stability to a joint. If any of these tissues become damaged, the joint will lose stability and may be more susceptible to injury.

Synovial fluid: Serves to lubricate the joint and provide nutrition to neighbouring cells maintaining joint cartilage, as well as removing waste products. Normal joint fluid is pale yellow in colour and oily — similar in consistency to car engine oil.

Related: Hidden Lameness: Is Your Horse Suffering in Silence?

Main Photo: Shutterstock/Brastock