Treatment of Lameness in the Horse

By Liz Devine DVM, MS, DACVS-LA, Pilchuck Veterinary Hospital

Lameness in horses can occur for a variety of different reasons. Most commonly, our equine athletes suffer from wear-and-tear type injuries that result from repetitive strains, like any human athlete performing at the top of their game. These repetitive strain injuries frequently manifest as joint disease or damage to soft tissue structures (such as tendons and ligaments). The successful treatment of these conditions relies on an accurate diagnosis and, in some cases, can require a few different treatment modalities for success.

Joint Disease

Synovitis and osteoarthritis are the most common joint diseases that we treat in the equine athlete. Synovitis is inflammation of the synovial lining in the joint. It is the result of daily repetitive trauma experienced by the joints of athletic horses. This inflammation causes pain and swelling and can lead to release of inflammatory cytokines and enzymes. If untreated, this eventually leads to permanent incongruity of the joint surface and
instability, which subsequently causes osteoarthritis. As in people with arthritis, there is no cure for this condition. However, there are multiple ways to manage it.

Systemic Treatment

Systemic anti-inflammatory therapy has been used for years to treat osteoarthritis. Medications such as Bute, Banamine, and Equioxx are very effective at reducing inflammation and helping decrease pain. However, as with any medications, these drugs can have systemic side effects and should only be used under the supervision of a veterinarian.

Systemic joint treatments are also available. Intravenous Legend is a systemic hyaluronic acid (HA) product that has been shown to benefit the joint at a cellular level. Because it is given intravenously, one injection will treat the entire horse instead of a single affected joint. Another systemic product, Adequan, is administered intramuscularly. This medication is a polysulfated glycosaminoglycan that has been shown to decrease cartilage damage when it is present in a joint. These products work on the joint by different mechanisms, so a veterinarian may recommend their use simultaneously or separately depending on the case. Both products are FDA approved.

Localized Treatment

In other cases, the veterinarian may determine that local therapy in the joint would benefit the horse. Many owners have heard of “joint injections,” but don’t necessarily know what that means or what is used to treat the joint. The most common medication for this type of treatment is a corticosteroid. Steroids are very effective
 
at decreasing inflammation, and therefore relieving pain, in the specific, targeted joint. HA is often combined with the steroid when injecting a joint (aka, intra- articular). HA naturally occurs in healthy joint fluid and cartilage but becomes depleted when there is inflammation. This combination of medications helps set up a healthier environment for the joint and has proved very effective for alleviating lameness in many horses that is due to synovitis and osteoarthritis.

Newer Therapies

While steroid and HA injections are often successful, in some cases they are ineffective for a particular horse or there are other confounding factors. In these cases, a veterinarian may recommend other therapies. One of these is called IRAP (Interleukin-1 Receptor Antagonist Protein). This therapy utilizes the body’s own anti-inflammatories contained in the blood. After processing IRAP from a blood sample in the lab, the vet can inject the IRAP into the joint to decrease pain and inflammation. Typically, this therapy is administered through three weekly injections into the joint. ProStride is a newer product on the market that also utilizes the horse’s own anti-inflammatories but does not require processing in a laboratory; it can simply be administered stall-side.

Tendon and Ligament Injury

Soft tissue injuries frequently cause extended lay-up periods for equine athletes. Sometimes a single over-strain or trauma can lead to a tear in the soft tissues; but, more commonly, it is a result of repetitive trauma. Repetitive trauma leads to small microtears in the tendons and ligaments, like the microtears that occur in muscles. However, whereas muscles are strengthened through that process, cumulative microdamage in tendons and ligaments can lead to a clinically significant injury. Ultrasound will often reveal a “core lesion” or tear in the center of the ligament. The body heals these tears with scar tissue, which is very strong but also quite inelastic. Normal function of a tendon requires stretching with every step that the horse takes, so an inelastic scar sets up the body for increased risk of re-injury adjacent to the original defect. Therefore, equine veterinarians work very hard to try to help the body generate a more functional scar.

Intralesional Therapies

Platelet rich plasma, or PRP, is a therapy that concentrates the horse’s platelets and other growth factors. In a procedure performed stall-side using ultrasound guidance, the concentrated growth factors are injected into the defect in the tendon. Stem cell therapy is also used intralesionally in tendons and ligaments. First, bone marrow or fat is harvested from the horse and then sent to a lab, where the stem cells are isolated and allowed to proliferate until the desired number of cells are cultured. The stem cells are then injected into the lesion in the tendon or ligament to lessen scar tissue and aid in healing. Shockwave therapy is used to induce microtrauma and to encourage new blood vessels into the injury site. This stimulates the body to heal the injury and can also provide some transient pain relief.

Many Therapeutic Options

Although lameness in horses can be very frustrating to deal with, it’s important to remember that your veterinarian has many therapeutic options available for treatment. Utilizing some of these therapies can help heal your horse and enable it to realize its athletic potential.