Joint wear and tear is a part of every equine athlete’s life. As your horse ages, joints naturally become stiff and sore – a process that is accelerated with heavy exercise.

Joint injections deliver medication directly to the affected joints. These injections are a reliable way to reduce pain and inflammation, supporting mobility and comfort in your horse.

Injections may be used to administer corticosteroids, hyaluronic acid, anti-inflammatory compounds, or platelet rich plasma. These treatments are most commonly used in horses with osteoarthritis, but may also be used to treat infections and other joint diseases.

While generally safe, there are some risks associated with injectable medications. These treatments can also be expensive and need to be repeated regularly to continue to work.

In addition to injectable therapies, there are many options to maintain joint health. Supplements, oral medications, exercise modifications, dietary strategies, topical treatments and bodywork are some of the modalities used to address joint issues in horses.

Consult with your veterinarian to determine whether joint injections are appropriate for your horse. Also, consider diet and management strategies to support your horse’s joint health and reduce reliance on pharmaceutical drugs.

Joint Injections for Horses

Most joint injections are administered intra-articularly, directly into the free space between the bones within the joint capsule.

There are three main reasons to perform intra-articular joint injections:

  • To block or anesthetize the joint in order to determine if a specific joint is the cause of your horse’s lameness
  • To sample lubricating fluid (or synovial fluid) in the joint and determine whether there is infection present
  • To introduce anti-inflammatory medications that reduce pain and increase range of motion

You and your veterinarian must take into account many considerations before deciding if joint injections are necessary for your horse. The type of injection used will depend on the intended purpose.

Joint Blocking

Anesthetizing or “blocking” the joint is a diagnostic tool used to identify where your horse’s pain originates from.

For example, let’s say you and your vet determine that your horse is lame in the hind end, but it is unclear whether the hock or the fetlock is the issue.

Your vet blocks the fetlock and asks to see your horse move again. If your horse is still lame, the source of the pain is not the fetlock. If your horse is now sound, the source of the pain is identified as the fetlock.

Synovial Fluid Sample

Synovial fluid is a clear, viscous liquid that provides lubrication and reduces friction in the joint.

If your horse is suffering from joint issues, your veterinarian may take a sample of the synovial fluid to determine the overall health of the joint. Your vet will examine:

  • Overall appearance of the fluid – the colour and thickness of the fluid can indicate infection or inflammation [1]
  • Protein concentration – too much protein can indicate infection or blood in the joint [1][2]
  • Nucleated cell count – an increase of cells with an obvious nucleus indicates infection [2]

Medicating the Joint

If your horse is experiencing soreness, intermittent lameness, or stiffness in a joint, your vet will likely suggest medicating their joint.

Before taking this step, your vet may perform flexion tests to determine which joints are causing pain. Your vet will hold your horse’s leg in a position that stresses one or multiple joints, then have the horse trot off in hand. This test allows the vet to see which joints become easily pained under stress.

Your vet may then take x-rays or perform an ultrasound on the suspected joint to visualize any arthritis or injury. Your vet may suggest medicating a joint if your horse is diagnosed with:

If you have a high-performance horse in heavy work, your vet may also suggest routine joint injections to maintain soundness.

Depending on how your horse reacts to treatment, your vet may suggest routine injections yearly, bi-yearly, or on an as-needed basis. It is not recommended to inject the same joint more than twice in one year. [3]

Joint Injection Treatment Options

Intra-articular joint injections are primarily used to:

  1. Ease any inflammation that is causing pain
  2. Assist in rebuilding the cartilage of a joint

The most common medications that your vet will inject into the joint are hyaluronic acid and corticosteroids.

Less commonly, your vet may choose to use Interleukin-1 Receptor Antagonist Protein (IRAP), Platelet Rich Plasma (PRP), or Autologous Protein Solution (Pro-Stride). [4]

Hyaluronic Acid and Corticosteroids

Hyaluronic acid (HLA) is a natural component of healthy joints, making up part of the cartilage and connective tissues.

Corticosteroids are a class of synthetic steroid drugs used primarily for their anti-inflammatory properties.

Whenever there is damage to the cartilage of a joint, the body responds by sending inflammatory signals to that site. This inflammation is what causes your horse’s joint pain.

A combination of hyaluronic acid and corticosteroids are used in some joint injections to reduce inflammation and ease your horse’s pain. [5][6] Research by Dr. Auer first established the efficacy of medicating joints with HLA.

In a 1980 study, Dr. Auer treated horses with chip fractures of the radial carpal bones of both front legs with a hyaluronic acid injection into one leg.

These horses showed a significant increase in weight-bearing on the injected leg, to the point where there was no observable lameness on that leg. This study led to the development of HLA and corticosteroid solutions used today.

Compared to other joint medications, hyaluronic acid and corticosteroid injections are less expensive. However, they do not influence the body’s ability to regenerate joint tissue. They are a temporary solution to provide pain relief and must be re-injected on an ongoing basis to maintain efficacy. [5][6]

Interleukin-1 Receptor Antagonist Protein (IRAP)

Interleukin-1 Receptor Antagonist Protein is a protein that your horse’s body naturally produces to reduce inflammation. IRAP is collected by drawing blood from your horse, incubating the blood over specialized glass beads, and injecting the solution directly into the joint. [7]

IRAP may stop the inflammatory process and trigger regeneration of the cartilage within the joint. Cartilage is a protective tissue that sits over the end of the bones where they connect to form a joint.

Cartilage is extremely smooth and allows the joint to move fluidly without friction or pain. If this cartilage is damaged or inflamed, your horse can experience pain. [7]

IRAP therapy promotes the healing of damaged cartilage. A recent study examined the effects of IRAP in joints that underwent arthroscopy.

Not only was there a significant increase in anti-inflammatory biomarkers, but also there was a reduction in the breakdown of hyaluronic acid in synovial fluid. [7]

IRAP injections are quite expensive, and are generally used only if hyaluronic acid and corticosteroid injections are not an option.

Platelet Rich Plasma (PRP)

Platelet Rich Plasma injections also use a solution derived from your horse’s own blood. Your vet will draw a volume of blood from your horse and process it in a centrifuge – a device that spins fluids at high speeds to separate out components.

The centrifuge separates platelets from the rest of the blood. Your veterinarian will then use these platelets to produce an injectable medication. [8]

Platelets contain growth factors that stimulate tissue regeneration and cell reproduction. Injecting these platelets directly into the intra-articular space assists in healing cartilage and reducing joint pain.

PRP injections are not only used for osteoarthritis, This therapy is also beneficial for tendon or ligament tears because it stimulates regenerative effects. [8]

Although studies are limited, promising early evidence indicates that PRP promotes tissue regeneration and reduces inflammatory markers in the synovial fluid. [8]

PRP injections can be very expensive. Your veterinarian will only consider this therapy if the damage to the joint is severe.

Autologous Protein Solution (Pro-Stride)

Pro-Stride therapy is also made using a derivative of your horse’s blood. This orthobiologic medication is made by processing your horse’s blood into a concentrated solution of platelets, growth factors, and anti-inflammatory cytokines. [9]

This autologous protein solution is then injected directly into the joint to address soft tissue injuries, reduce inflammation, and slow cartilage degradation. Pro-Stride protects the joint from damage and alleviates pain. [9]

In addition to osteoarthritis, Pro-Stride has been used to treat bursitis, tendinitis, partial ligament ruptures, bowed tendons, lumbosacral stenosis, patellar luxation, joint laxity, osteochondral dissecans. [9]

Most research into the efficacy of Pro-Stride has been conducted on dogs with ligament ruptures. Based on these promising results, researchers intend to further study the use of Pro-Stride in equine osteoarthritis. [9]

The two-step process to make Pro-Stride is proprietary and comes with a high price tag. Although initial research suggests this treatment is effective, Pro-Stride may not be an option for everyone’s budget.

Administering Joint Injections

The process of administering joint injections to your horse is the same regardless of the medication chosen. Injections should only be administered by a trained equine healthcare practitioner.

For easily accessible joints, such as the hocks, knees, and stifles, injections are generally performed at your farm. To prepare for the procedure, make sure that the treatment area is cleaned in advance and minimize the number of people or horses walking around.

Choose a well-ventilated lotcation. Any residual dust in the air can contaminate the injection site and increase the risk of infection.

Procedure

Your veterinarian will sedate your horse and clip the hair around the area they intend to inject. The veterinarian or an assistant will then scrub the injection site thoroughly with an antiseptic solution, working from the centre of the area outwards. They will repeat this process for approximately 10 minutes.

Your veterinarian will then twitch your horse to ensure they stay still for the remainder of the procedure. They will then put on sterile gloves and insert a sterile needle into the joint.

Don’t be alarmed if clear fluid leaks out of the needle. This is the synovial fluid that naturally occurs in the joint. [3]

Aftercare

After the injection, your veterinarian will immediately place a bandage on the site. Your horse will need to remain on stall rest for the next 24 hours with no turnout or exercise.

Some veterinarians recommend you hand-walk your horse periodically the following day. It is not recommended to ride your horse immediately after a joint injection.

Your veterinarian may suggest you administer NSAID medications such as Flunixin Meglumine (Banamine) or Phenylbutazone (Bute) to control any pain and inflammation. [4]

If your horse exhibits any heat or lameness of the area, let your veterinarian know as soon as possible. Heat and lameness could indicate serious infection that needs to be addressed immediately.

Risks of Joint Injections

Although rare, infection is a major concern with joint injections and synovial sampling. Inserting a needle into the joint space could introduce bacteria that can multiply quickly and cause serious issues.

Symptoms of joint infection includes:

  • Extreme lameness of the injected limb
  • Heat and swelling of the joint
  • Fever

These symptoms are usually observed 7-10 days after the injection, but can occur at any time. Call your vet at the first sign of anything, as joint infections can be life-threatening.

Some vets choose to inject antibiotics along with medication in order to reduce the likelihood of infection. [4]

Adjunct Therapies

To optimize the effectiveness of joint injections, it is important to make sure your horse has the proper nutrition to keep joints healthy.

Ensure that your horse is maintained at a healthy body condition. Carrying excess bodyweight puts added strain on the joints.

Always feed your horse a balanced vitamin and mineral supplement to avoid common deficiencies in the diet. Key nutrients for collagen synthesis and joint health include copper, zinc, Vitamin D, selenium, iodine and Vitamin C.

Methylsulfonylmethane (MSM)

MSM is a very well-researched and well-tolerated joint supplement that can be added to most feeding programs.

MSM is a source of the mineral sulfur, which is an important component of glucosamine and collagen. These are two proteins that make up connective tissue.

Research shows that MSM supports joint health by:

  • Acting as an antioxidant to reduce cell-damaging free radicals
  • Inhibiting cholinesterase, an enzyme that promotes muscle spasms and joint pain
  • Decreasing the level of inflammatory compounds in the body [10]

In a study of horses involved in jumping competitions, feeding MSM reduced oxidative stress and exercise-induced inflammation. [10] MSM is an inexpensive and effective way to reduce inflammation and protect your horse’s joints.

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Glucosamine and Chondroitin Sulphate

Glucosamine and chondroitin sulphate are ingredients commonly used in joint health supplements, but there is mixed evidence of efficacy.

In some animal studies feeding glucosamine and chondroitin sulphate has been shown to slow the degradation of cartilage, increase the quality of synovial fluid, and promote anti-inflammatory effects.

However, studies indicate that these substances have very low oral bioavailability. They must be fed in high concentrations to be absorbed by the blood. More evidence is needed to establish effective dosages of glucosamine and chondroitin sulphate. [11]

Omega 3 Fatty Acids

Feeding essential omega-3 fatty acids can reduce inflammation in the joints and increase your horse’s comfort.

Studies show that horses supplemented with the omega-3 docosahexaenoic acid (DHA) have reduced inflammatory markers and reduced expression of cartilage degrading enzymes. [12]

In one study, horses fed DHA for 75 days had longer stride lengths compared to unsupplemented horses, suggesting improved mobility and joint comfort. [13]

However, not all omega-3’s are equally effective. Alpha linolenic acid – found in flax and camelina oil – is not as effective as DHA and EPA, which are the omega-3’s found in fish oil.
[12]

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Summary

Talk to your veterinarian if you think your horse may benefit from joint injections.

Your veterinarian will likely suggest additional supplements and strategies to support your horse’s joint health alongside injectable medications.

For more suggestions, read our article on the 8 Key Principles for Supporting Joint Health in Horses.

Is Your Horse's Diet Missing Anything?

Identify gaps in your horse's nutrition program to optimize their well-being.

References

  1. Forsyth, S. Equine synovial fluid analysis. VetScript. 2018.
  2. MacWilliams, P. and Friedrichs, K. Laboratory evaluation and interpretation of synovial fluid. Vet Clin North Am Small Anim Pract. 2005.
  3. Steel, C. Equine Synovial Fluid Analysis. Vet Clinics of NA: Equine Prac. 2008.
  4. Caron, J. Intra-Articular Injections for Joint Disease in Horses. Vet Clinics: Equine Prac. 2005.
  5. Auer, JA. et al. Effect of hyaluronic acid in naturally occurring and experimentally induced osteoarthritis. Am Journal of Vet Research. 1980.
  6. McIlwraith, C. The use of intra-articular corticosteroids in the horse: What is known on a scientific basis? Equine Vet Journal. 2010.
  7. Machado, T. et al. Effects of blood-derived products and sodium hyaluronate on equine synovial fluid cells and on synovial fluid from osteochondrotic joints of horses after arthroscopy and administration of treatment. Am Vet Med Assoc. 2019.
  8. Textor, J. et al. Synovial fluid growth factor and cytokine concentrations after intra-articular injection of a platelet-rich product in horses. The Vet Journal. 2013.
  9. King, W. et al. The Use of Autologous Protein Solution (Pro-Stride®) and Leukocyte-Rich Platelet-Rich Plasma (Restigen®) in Canine Medicine. Vet Med. 2021.
  10. Marañón G. et al. The effect of methyl sulphonyl methane supplementation on biomarkers of oxidative stress in sport horses following jumping exercise. Acta Vet Scand. 2008.
  11. Hanson, R. et al. Oral Treatment With a Glucosamine-Chondroitin Sulfate Compound for Degenerative Joint Disease in Horses: 25 Cases. Orthopedics. 1997.
  12. Hess, T. and Ross-Jones, T. Omega-3 fatty acid supplementation in horses. R Bras Zootec. 2014.
  13. Woodward, AD. et al. Supplementation of dietary long-chain polyunsaturated omega-3 fatty acids high in docosahexaenoic acid (DHA) increases plasma DHA concentration and may increase trot stride lengths in horses. Equine Comp Exerc Physiol. 2007.