Lameness and the SA endurance horse
Dr MG Walton Ceres Veterinary Hospital
Lameness is the most
common reason for elimination in endurance worldwide.The incidence of lameness increases in proportion to the distance travelled and the degree of tiredness of the horse and rider. Thankfully, lameness is usually mild and most often resolved within a day or two.
Sole bruising and corns - one of the most Spasms of the hind quarters can be cause severe pain. common causes of temporary lameness.
What is lameness? “A consistent irregularity of gait with or without obvious pain which, in the opinion of the examining veterinarian, will be worsened by continuing the ride or will cause further injuries to develop or will be detrimental to the future soundness of the horse.”
The speed required to win has increased dramatically over the past 10 years. Due to the speed increasing, we are starting to see injuries more like those seen in the flat racer, as well as serious metabolic problems. Horses trend to be pushed harder with the larger prize money at stake.
Two categories of lameness are identified in endurance horses:
In terms of training, over-training of endurance horses tends to be more of a problem than under-training, particularly in novice riders.
Transient problems that may be cause for elimination, but are resolved within a short period of time More persistent problems that are likely to be recurrent (chronic lameness).
However, this can be oversimplification as some injuries or causes of lamenesses can fall or develop into both categories. Why Is Lameness The Most Common Cause Of Elimination? Endurance by its very nature causes repetitive concussion (jarring) of the lower limbs which may cause damage to the coronary band or joints, particularly to the fetlock joints. Tendon and ligament damage is less common. Hind limb damage often relates to muscular damage, ER and distal hock pain. Thankfully, laminitis is rare in the endurance horse. Chronic lameness contributes to rapid exhaustion.
Lameness Work-up Your veterinarian has a number of techniques to diagnose the problem and the specific cause of the pain. The horse is trotted out at different speeds and on different surfaces in both circles and straight lines. Hoof testers are used to try and find painful areas in the hoof. The leg is then carefully palpated (felt) for any signs of heat, pain or swelling.The vet may also use nerve blocks – injecting local anaesthetic over specific nerves to try and determine where the pain is coming from.They may also zone in on specific bone or soft tissue areas using radiography (X-rays) or ultrasound scanning. More modern techniques for imaging, including CT scanning and scintigraphy, are also now available for horses. If a diagnosis cannot be reached, the horse will often be re-evaluated in two to four weeks.
Conformation is important A toed-in horse (hooves pointing inward) could develop splints that begin to press on the suspensory ligament, causing recurring pain and making these horses ultimately unsuitable for endurance use.
Here is a summary of the most common conditions causing recurrent lameness in endurance horses:
Terrain plays an important role in lameness development. On rocky ground, more horses have stone bruises and painful concussive joint injuries, whereas on softer sandy ground we may see more ligament and tendon injuries.
Foot/hoof problems are a frequent cause of elimination from a ride and of recurring pain. Problems are more common in the front hoof as 65% of the horse’s weight is carried by the front limbs. Inflammation and bruising of the sole on the rough ground, trapped stones as well as shoe loss and shifting of the shoe are
typical causes of lameness. A shortened choppy gait is typical, with pain elicited by hoof testers at the site of injury. The importance of a properly balanced, well-trimmed hoof cannot be over emphasised! Due to the continual impact of endurance, imbalance can have a significant effect on support structures of the limb. Hoof shape such as long toe, low heel syndrome puts increased strain on the supporting tendons! Sore feet often occur in horses in combination with sore back and hock pain – the socalled “terrible triad”! Management of hoof injuries involves correct trimming and conditioning, protecting the sole and reducing concussive forces. Problems are more common in the front hoof as 65% of the horse’s weight is carried by the front limbs. Distal Hock Pain Pain in the lower hock joint of the hind leg is common in the endurance horse. It is often bilateral (both sides) and fluid in the joint (joint effusion) is not always obvious. They are often positive to flexion tests. X-ray changes do not always correlate with the clinical signs. Distal hock pain frequently occurs together with paravertebral myalgia and sore front hooves, the terrible triad. This probably results from the horse with sore front feet altering the gait in such a way as to cause strain on the paravertebral muscles and hocks. The best results are obtained when all three problems are addressed simultaneously. Otherwise, the pain in one area and gait alteration in another area becomes a neverending cycle. Distal hock pain frequently occurs together with back pain and sore front hooves Osteoarthritis or DJD (degenerative joint disease) of the Fetlocks Arthritic changes in bone and cartilage of the fetlock joint is one of the most common causes of pain and lameness at the Fauresmith 200 km in South Africa. The continual stress on the joint in these marathon horses causes degeneration of the joint, particularly in older horses. It can occur in one or more joints and does not always cause obvious pain and fluid inside the joint. Flexing the joint often causes pain and the joint may have a reduced range of motion caused by the chronic (long-term) thickening around the joint. Fetlock DJD is diagnosed using X-rays but, interestingly, the degree of changes does not always correlate to the degree of lameness. Treatment options include injection directly into the joint with cortisones or joint protectants such as glycosaminoglycans and hyaluron. Rest, ice and anti-inflammatories may complement a neutraceutical supplement containing glucosamine, chondroitin and MSM in the food. Suspensory Desmitis One of the leading causes of recurrent lameness in endurance horses is proximal suspensory desmitis (inflammation of the beginning of the suspensory ligament on the back of the leg). This is more likely to develop in the later stages of a ride when the horse is fatigued, but can occur earlier on in an unfit horse. Pain can develop suddenly, or be more insidious. Often little
swelling occurs but palpation and flexing the leg may cause pain. Ultrasound is the favoured method to diagnose this condition which may be bilateral or affecting both sides. There may be inflammation without detectable changes on ultrasound yet. (Fewer ultrasound changes carry a better prognosis or chance of recovery.) The lameness is treacherous as it will often respond to a short rest, the rider gets a false sense of security and the horse is returned to work again only to become lame once more. If there are substantial changes, work should be avoided for at least eight months. Treatment involves triamcinolone, anti-inflammatories, ice and bandaging. Horses should be walked in hand until no lameness is apparent when trotting on a hard surface with no antiinflammatories. Begin training gradually in a controlled manner over eight to 12 months. This routine has been used for hundreds of years but is still as relevant as ever. “The reason conventional wisdom becomes conventional wisdom is that it has withstood the test of time!”
Fortunatley, fractures are rare in endurance.
Athrtitis of the fetlock joint is one of the most common causes of chronic lameness in endruance.
Superficial digital flexor (SDF) tendonitis SDF tendonitis (inflammation of the outermost tendon flexing the foot) may be acute (rapid developing) or chronic, mild or severe. The tendon may be warm and swollen, but, interestingly, lameness is not always apparent. Horses sustaining a partial or complete rupture of the tendon have a poor prognosis or chance of full recovery. Ultrasound is essential to determine if fibre damage has occurred and to determine the degree of swelling and damage. Initial management is aimed at preventing further damage, reducing swelling and inflammation and relieving pain. Rest, ice, anti-inflammatories and bandaging are usually prescribed. Some
vets advocate surgery as part of the tendon management. Regular scans help map the improvement and can be used to determine when to commence exercise. Exciting new developments include the injection of stem cells, platelets and other products into the site of the injury to improve the speed and quality of tendon recovery. Exertional Myopathy (EM) – “tying up”_ EM is most often seen at the beginning of a ride and should be viewed as part of a larger picture involving fatigue and metabolic abnormalities. Symptoms include stiffening of hindquarter muscles, shortening of stride, trembling, sweating and dark, discoloured urine. This is a potentially life-threatening condition that should receive immediate veterinary attention! (This complex topic will be covered in a future article in this magazine.) Gluteal Myalgia (GM) – “spasms of the hindquarters”
Tendon injuries can be catastrophic.
Inflammation of the gluteal (hindquarter) muscles occurs commonly in endurance due to the strenuous work over long distances.The muscles are painful with swelling and even asymmetry apparent in the early (acute) stages. Most horses respond to anti-inflammatories, physiotherapy and two to three weeks rest. Gluteal muscle pain often occurs with forelimb lameness because horses alter their hind limb gate to protect themselves. It is important to try and identify and treat the primary forelimb pain. Paravertebral Myalgia (PM) – “ back spasms” Paravertebral myalgia (pain of the muscles along the spine) is caused by a fatigued, unbalanced rider. Unfortunately, diminished rider capability often occurs simultaneously to the horse experiencing its own muscle fatigue. A fit, experienced rider subjects less battering to the back muscles than a novice rider. Similarly, a fit, balanced rider able to adjust their weight distribution will batter back muscles less than a dead weight such as lead weights. Horses with this condition appear stiff and rigid and instead of flexing and extending the spine normally when palpated, they tend to squat or crouch. PM may also occur in horses that have altered their gate due to sore hooves or hocks. Treatment involves removing the inciting cause (eg, treating sore hooves), rest and anti-inflammatories. Complementary therapy such as physiotherapy, acupuncture and massage therapy also plays a role in therapy. A fit, experienced rider subjects less battering to the back muscles than a novice rider. Lumbosacral and Sacro-iliac (lower back) pain Lumbosacral and sacro-iliac pain occur in endurance horses due to the typical repetitive stress. Rider fatigue and their diminished capability to ride in a balanced manner play an important role in pain development. Muscle spasm is likely to exacerbate any existing instability in the sacro-iliac region. Horses exhibit shortness of stride, and pressure over the SI area elicits pain. Treatment involves manipulation and deep muscle massage to alleviate the spasm, anti-inflammatories and rest.
An X-ray of a normal healthy fetlock.
Inflammation (periostitis) and bony swelling (exostosis) of the splint bones is usually a nuisance problem that needs a four- to six-week break from training. X-rays should be taken to rule out fractures of the splint bones. Ice, anti-inflammatories and bandaging can help to reduce the inflammation. Most splints resolve with time and treatment, although a non-painful enlargement often remains. If the splint continues to enlarge, it may begin to interfere with the tendons and longer rest periods or even surgery may be required.
The ever-controversial topic of joint supplements will be covered in the next edition. Watch this space! Dr Marc Walton BSc (Agric), BVSc