AQHA November / December 2019 Magazine AQHA NOV-DEC 2019 PRINT (2) | Page 23

Locking STIFLES... Signs can be more pronounced at the start of exercise, and milder cases may move completely normally once warmed up. Common signs include stumbling in the hind end (which can lead to stumbling in the front end and occasionally falling). Horses may have difficulty cantering in one or both leads, and often have very awkward canter-trot and canter-walk transitions. Horses may become hesitant performing tasks they usually perform with ease. Because patella locking is a mechanical issue and the degree of pain varies, it’s important to seek veterinary advice to exclude other problems such as spavin or ringbone – which may also be present. Delayed patellar release can lead to lameness in the stifle - increased friction of the patella against the femur can cause joint inflammation, and the patellar ligaments are sometimes strained or stretched. Radiographs, ultrasound, scintigraphy or arthroscopy may be needed to rule out other conditions. Fatigue in young horses and those training intensely in cutting and dressage; lack of extended trotting work in Western pleasure horses and exercising in an inverted or hollowed-out position, all lead to poor patella function, muscle tiredness, altered co-ordination and changes in the development of the quadriceps and biceps muscles. Hind foot balance can also be a predisposing factor - low heels, elongated toes, upright inner hoof walls, long toe- low heel and lack of heel contact alter the flight and arc of the foot. To assess balance, draw a line following the coronary band of the hind hoof over to the front leg – the line should intersect with the front chestnut. With low heels and long toe-low heel hoof conformation the line will intersect closer to the elbow or even the girth region. Veterinary xrays may be necessary to assess the position of the coffin bone and the depth of the sole. This will help guide hoof balance correction, trimming and wedges. Upright conformation of the stifle is a risk factor because the patella to sits higher and the medial trochlear ridge is directed more forward instead of upward. Another contributory factor is long patellar ligaments due to the increased risk of strain and over-stretching. The release of the patella relies upon the quadriceps and biceps to pull it sideways and upward, so lack of fitness and reduced or poor muscle tone in the quadriceps or biceps increases the risk. Lack of fitness can occur in rapidly growing horses that have not yet fully developed muscling and co-ordination, in retired or sedentary horses, or horses returning to work after a spell. Veterinary investigation and assessment is important to rule out conditions such as stringhalt (which causes exaggerated jerking movements of the hind legs), fractured bones, foot abscesses and other causes of abnormal gait in horses. Treatment options - may include hormone injections, internal blisters, ligament splitting or surgery and joint therapy. For some horses, improving fitness and incorporating extended trot, swimming, walking and trotting up hills (but not down), over poles and in deep, sandy or loamy soils will get those hindquarters pumping and can lead to resolution. Lunging, working in tight circles and round penning are not recommended. An altered range of motion can also occur in horses that have a lameness due to hindlimb, hock or back pain which lead to loss of normal quadriceps and biceps muscle tone and changed coordination. Neurologic conditions such as wobblers or damage to the nerves that supply the quadriceps and biceps can lead to loss of overall muscle tone and strength, predisposing to delayed release of the patella. And stifle OCD can affect the gliding surface of the patella, the trochlear ridges on the femur and the patella itself. Corrective farriery is often beneficial - trimming the inside wall and lateral heel extensions encourage a wider stance and loading down the outside of the leg; raising the heel and rounding the toe improves breakover; wedge pads help limit the degree of stifle joint extension. For horses that are light in condition, relief can come from weight gain which increases the size of the fat pad that lies beneath the patella. Ensuring protein and amino acid intake is correct will assist muscle building and strength and the response to training. Sudden changes in management and exercise or a downhill top line also increase the risk. Horses with this conformation must extend the hind limbs further under the body to accommodate the forward transfer of weight, thereby increasing the likelihood for inadvertent fixation of the patella. Insufficient foot angle can increase the degree of pelvic limb extension, increasing the likelihood for patellar fixation, and abnormal structure, inflammation and pain of the stifle joints all increase the risk. It is not uncommon to have a lameness problem somewhere else in the limb, such as the hocks, which can be a contributing factor in the development of delayed patellar release - in these cases, treatment directed at several areas may be necessary. Upward fixation of the patella is one of the main conditions affecting the stifle – accounting for 15% of hind limb lameness. In one study that reviewed treatments, 40% of horses with locking stifles showed complete recovery, and 20% had marked improvement following corrective shoeing. Another 10% of affected horses showed improvement when corrective trimming was combined with weight gain and exercise. If these don’t resolve the problem, surgery may be required. Horses that regularly suffer from locking stifles and don’t achieve a normal gait after a few strides may not be safe to ride. To achieve the best outcome get a veterinary opinion as soon as possible. F All content provided in this editorial is for general use and information only and does not constitute advice or veterinary opinion. The content does not consider individual circumstances, is not intended as a substitute for advice, and should not be relied upon as advice or in place of consultation with your equine veterinarian. For full disclaimer, please refer to our website: www.jenquine.com.au NOVEMBER/DECEMBER ISSUE 2019 PG.21