Lameness in the horse can range from an obvious non-weight-bearing gait to more subtle signs of discomfort that may only be displayed as poor performance. The goals of a lameness examination are to identify the affected leg and the exact part of it that is causing the lameness.

Before watching the horse move, your vet may want to know about his recent activity. The horse should be examined from a distance and up close, with a thorough palpation of the legs. As the vast majority (up to 90 percent) of all lamenesses originate in the foot, the hoof, sole and heels should be carefully assessed; applying pressure around the foot with hoof testers can help to detect any pain. Finally, the horse can be observed at the walk and trot, both in a straight line and on a circle, to look for signs of lameness.

The area of origin can be more closely isolated with flexion tests, placing pressure on a joint in the leg by flexing it; lameness often worsens after flexion.

To further pinpoint where the pain is coming from, a diagnostic nerve block can be used, where a local anesthetic is injected to numb a portion of the leg. The horse is then jogged again to see if the lameness has improved or resolved. These procedures are started at the heel/hoof and progress up the leg until the area of pain is identified.

Next, diagnostics such as radiographs (X-rays), ultrasound and even more detailed scans, including computed tomography (CT) or magnetic resonance imaging (MRI), can be employed to determine the exact cause of the lameness.

Here are the top five causes of lameness.

Foot Abscess

Subsolar abscesses, localized infections just beneath the sole of the hoof, are one of the most widespread causes of foot pain. As an abscess develops, it exerts pressure on the sensitive structures of the foot.
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Navicular Syndrome

The navicular bone is a small canoe-shaped bone that lies within the hoof behind the coffin and short pastern bones. Navicular syndrome is a term used to describe the heel pain and pathology of navicular disease.
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Heel Pain

While heel pain is a component of navicular syndrome, it is very important to point out that there are a multitude of other structures in the hoof that can cause heel pain, such as the suspensory ligament of the navicular bone, the impar ligament that connects the navicular bone to the back of the coffin bone, and other collateral ligaments.
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Degenerative Joint Disease

Degenerative joint disease (DJD) is a common occurrence in older, and sometimes not so old, equine athletes. The body is designed to maintain the cartilage in the joints, repairing damage after normal wear and tear. In athletic horses, however, excessive wear can overwhelm the repair process.
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Tendon and Ligament Injury

There are several important tendons and ligaments in the lower leg. The superficial digital flexor tendon, the deep digital flexor tendon, and the suspensory ligament are the most prominent and often prone to injury.
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While it is impossible to list all the ways why horses can go lame, it’s useful to understand some of the top causes. Knowing how these injuries and diseases present will allow you to better recognize a problem and start appropriate treatment sooner so that you can get back in the saddle.

The Lameness Scale

The American Association of Equine Practitioners has developed a grading scale (0-5) so that all horsemen and veterinarians can use the same criteria for describing a lameness.

• Grade 0: A sound horse .
• Grade 1: Lameness that is difficult to observe and is not consistently apparent.
• Grade 2: Lameness that is difficult to observe at a walk or when trotting in a straight line, but consistently apparent under certain circumstances.
• Grade 3: Lameness that is consistently observable at a trot under all circumstances.
• Grade 4: Lameness that is obvious at the walk.
• Grade 5: Lameness that produces minimal weight bearing in motion and/or at rest, or a complete inability to move.

Liked this article? Here’s more on equine lameness:

Managing Mystery Lameness
Hoof Care and Lameness Topiclist

JOAN NORTON, VMD, DACVIM, is the founder of Norton Veterinary Consulting and Education Resources, a firm dedicated to the education of horsemen and equine veterinarians through internal medicine consultations, lectures, webinars and writing. More information on her services and courses can be found at
www.nortonveterinaryconsulting.com.

This article originally appeared in the June 2014 issue of Horse Illustrated. Click here to subscribe!

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Horses with abscesses may show varying signs of lameness, but it is often an acute onset of a significant degree of pain, sometimes as severe as Grade 5 lameness (see “Lameness Scale”). These horses may have heat in the foot and an increased digital pulse felt at the fetlock or pastern.

Diagnosis of a hoof abscess is typically straightforward, and identification of the precise location is usually easily achieved with hoof testers. Occasionally radiographs are required to pinpoint the location of the abscess and the extent of its damage, as large or chronic abscesses may infect the coffin bone.

Treatment involves relieving the pressure by draining the abscess. Using a hoof knife, your veterinarian can carefully pare down the sole until the pus can escape. If the sole is too hard, then the foot can be soaked in warm water and Epsom salts for several days to soften the area. Abscesses may also break out through the coronary band, taking the path of least resistance. This area should be monitored closely in these cases.

There are many factors that contribute to the development of hoof abscesses, such as an environmental shift from wet to dry footing; hard ground that bruises the sole; dirty, wet stalls; improper shoeing; or poor hoof conformation. Prevention involves keeping horses in clean conditions and performing routine hoof care, such as daily cleaning and regular trimming.

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Radiographs don’t always solve the riddle, as they do not give information about these soft tissue structures. In recent years, magnetic resonance imaging (MRI) has become the gold standard for diagnosing lameness of the equine foot. MRIs provide information about both the soft tissue and bone structures in great detail, and many horses who would have been classified as having navicular syndrome are found to have other problems within the foot.

While many of the treatments for soft-tissue heel pain are similar to those used for navicular syndrome, thorough diagnosis is the only way to ensure proper treatment. Diseases of the collateral ligaments in the hoof improve greatly by using specialized shoes to more evenly distribute the weight across the hoof. Not knowing the exact cause of your horse’s heel pain may lead to improper shoeing techniques and a delayed return to full function.

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Degenerative Joint Disease
Degenerative joint disease (DJD) is a common occurrence in older, and sometimes not so old, equine athletes. The body is designed to maintain the cartilage in the joints, repairing damage after normal wear and tear. In athletic horses, however, excessive wear can overwhelm the repair process. As forces of movement and impact cause trauma to the cartilage, there is inflammation and an increase in blood flow to the area. This leads to heat and swelling and brings inflammatory enzymes to the joint, which further work to degrade the cushioning cartilage. The result over time is a net loss of cartilage, the hallmark of DJD.

The signs of degenerative joint disease include lameness, which can range from mild to severe; heat and swelling around a joint; and sometimes a reduced range of motion of the joint. These signs can progress slowly or show up acutely once your horse’s pain threshold has been exceeded.

Diagnosis of DJD, once the joint in question has been identified, involves radiography. X-rays will show a decreased joint space, and changes in density and remodeling of the bone in advanced cases.

Management of DJD should be aimed at early intervention and maintaining a healthy population of chondrocytes by reducing inflammation. Chondrocytes (cells that create cartilage) that are kept healthy through rest and the appropriate therapies will continue to repair the damage. Once these cells are lost, however, there is no reversing the process or creating new cartilage.

Changing the horse’s training program to decrease joint trauma will help but isn’t always feasible. Anti-inflammatories such as phenylbutazone (bute), firocoxib (Equioxx) or flunixin meglumine (Banamine) can block the production of the damaging inflammatory enzymes but should be used judiciously as they can have serious side effects on the GI tract and kidneys.

Chondroprotective products such as polysulfated glycosaminoglycan (Adequan) can decrease inflammation, reduce pain and encourage production of cartilage and joint-lubricating fluid. They are only effective if there is some cartilage left. Products that contain hyaluronic acid can mediate inflammation and improve joint function but may not be as effective in promoting new cartilage growth. Joints can also be injected with anti-inflammatory medications such as corticosteroids that will very effectively decrease inflammation, though they do not heal damaged cartilage or aid in new development.

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Diagnosis of these injuries involves the previously described techniques to localize the problem. The best way to evaluate the tendons and ligaments of the lower leg is through ultrasonography, which displays the intricate linear fiber pattern of the tendons and ligaments to show disruption or swelling in the structures.

Because tendons and ligaments have a very limited blood supply, they are difficult to target with therapeutics, so healing can be slow. Conservative options include stall rest, limited activity and anti-inflammatory medications. Shockwave therapy employs powerful acoustic energy directed at a focal point to increase blood flow and boost the natural healing process. Horses with suspensory ligament injuries show faster healing when shockwave is used; however, this treatment’s overall effectiveness has not been universally demonstrated, and not all experts are convinced it works.

Advances in regenerative medicine are the newest methods being used for tendon and ligament injuries. Injecting platelet-rich plasma (PRP) directly into the injured area will increase the amount of local growth factors that will promote healing.

Injection of stem cells into a lesion can provide a cellular scaffolding on which healing can begin. Both PRP and stem cells can be harvested from your own horse, making them safer and less likely to cause a reaction. Because they are from the body’s own cells or plasma, they do not trigger an immune response or inflammation.

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A: The term “cyst” is a misnomer; it means there is a “closed sac, having a distinct lining that is filled with fluid or air.” Bone cysts should be more appropriately called cyst-like lesions and are often referred to as subchondral bone cysts, as they are a disruption of the bone just beneath the cartilage within a joint.

Most commonly, bone cysts are a result of a developmental defect that occurred early in a horse’s life as the bone formed. Large-boned, fast-growing horses can have abnormal growth and mineralization of the cartilage that lines the joint surface. This can lead to defects in the deep layers of cartilage, and abnormalities of the cartilage within the joint. Imbalances in the calcium-phosphorus ratio of a young horse’s diet, as well as deficiencies in copper and excesses in zinc concentrations, can also cause these developmental abnormalities. Large lesions will cause lameness early in a horse’s life; however, smaller, more subtle changes will not cause a problem until the animal is in work, which is likely the case with your horse. The mechanical trauma of regular exercise will cause disruption of the improperly formed cartilage. Joint inflammation, cracks in the cartilage (arthritis) and even microfractures of the underlying bone can all occur with subchondral cysts.

Bone cysts are mainly diagnosed with radiographs. Equine sports medicine experts also use magnetic resonance imaging (MRI) to diagnose bony problems, as well as injuries to the delicate surrounding tendons and ligaments. There may be multiple pathologies causing the lameness that cannot be seen on radiographs alone.

Treatment of cyst-like lesions is mainly based on reducing the inflammation caused by the associated arthritis in the joint. Stall rest may allow the inflammation to quiet down, and can be an effective treatment in young horses. In older horses with concurrent osteoarthritis, rest has only limited success.

Ensuring that your horse is properly shod can also have an impact on his soundness; long toes and under-run heels can exacerbate lameness. Toe length can be shortened, and wedge pads can compensate for low heels.

Combating the inflammation within the joint will resolve the lameness in many cases. Intra-articular injections of anti-inflammatory corticosteroids and joint lubricating medications, such as hyaluronic acid, can improve joint function. These injections will improve soundness, but the treatments will need to be repeated based on your horse’s response.

Intramuscular injections of Adequan (polysulfated glycosaminoglycan) will support the health of the chondrocytes (cartilage cells), preventing further degeneration and improving the health of the joint. Surgical procedures do exist to treat cyst-like lesions and smooth out the arthritic changes seen on the cartilage, but they’re not always appropriate for every case.

Unfortunately, once cyst-like lesions associated with lameness are identified, there is little that can be done to cure them or reverse the arthritic changes that come with them. Being in tune with your horse’s comfort level and working closely with your veterinarian are the keys to a long and sound career for you and your horse.

Joan Norton, VMD, DACVIM, is the founder of Norton Veterinary Consulting and Education Resources, a firm dedicated to the education of horsemen and equine veterinarians through internal medicine consultations, lectures, webinars and writing. More information on her services and courses can be found at www.nortonveterinaryconsulting.com.

This article originally appeared in the November 2013 issue of Horse Illustrated. Click here to subscribe.

The post Ask the Expert: Subchondral Bone Cysts appeared first on Horse Illustrated Magazine.