Common Lameness Conditions in Horses Forelimb
There are numerous conditions which may cause pain and therefore lameness in the forelimb of the horse. These may vary according to breed, conformation, the type and intensity of activity as well as the surface upon which they are worked. However there are some common conditions which are seen on a more regular basis than others and these are outlined below.
Bucked Shins (3rd Metacarpal Periostitis)
Bone has an outer layer covering it which is called the periosteum. Certain conditions can cause the periosteum to become inflamed. This is termed Periostitis. The cannon bone (3rd metacarpal) or shinbone of the foreleg is the most commonly affected. Pain in the region of the front facing middle third (cranial mid-diaphyseal region) is caused by concussion which leads to small compression or stress fractures of this part of the cannon bone. The condition is similar to shin splints seen in humans.
Signs of bucked shins include warm, painful swelling over the areas affected and this condition occurs more commonly in young horses than older ones.
Distal Suspensory Ligament Sprain
The distal (furthest from the body) part of the suspensory ligament runs down the back of the fetlock from the carpus (knee) to the coffin joint. It is an important support structure preventing over-extension of the fetlock. The condition is caused by either a sprain or rupture of the ligament leading to inflammation. The damage occurs when the fetlock is hyper extended and stretched down towards the ground.
Hyper extension of the fetlock occurs during galloping or when working in soft-going, like mud or deep sand. It is a common injury in both Standardbred trotters and Thoroughbreds whilst the other nearby support tendons can also be injured at the same time (flexor tendons and check ligament). Signs of the condition are a significant lameness which can lead to chronic unsoundness sometimes permanent.
The splint bones (2nd and 4th metacarpal bones) are the small bones that lay on either side of the 3rd metacarpal or cannon bone. The second metacarpal is on the inner (medial) aspect of the limb and the 4th metacarpal is on the outer (lateral) aspect. This condition most often affects young horses and the inside splint bone is more commonly affected. The cause of splint problems is generally due to mechanical trauma and concussion for instance working on hard surfaces and poor conformation (bench knees). Strenuous training, as well as accidents occurring during rough play at pasture (e.g. jumping), can be responsible. The condition is not due to damage to the bones themselves but to the ligament that knits the splint bones to the cannon bone. This damage results in inflammation of the ligaments and incites new bone formation associated with periostitis. This process manifests itself as swelling and pain over the affected splint bone which causes lameness in that limb.
Tendon damage is caused by overextension of the lower part of the leg. The flexor (deep and superficial) tendons lie along the back (caudal) aspect of the cannon bone and provide the majority of support to this region. Tendons have fantastic elastic properties and are designed to recycle much of the energy the horse expends during exercise. Just like a rubber band however, they have their limits and overextension can cause serious damage.
Damage to the tendons is characterised by severe inflammation of the tendon seen as heat and swelling of the affected area. First aid treatment involves minimising the inflammation by cold hosing and the application of ice packs to the area. Your veterinary surgeon will also advise on the administration of anti-inflammatory therapy and appropriate shoeing techniques e.g. wedges.
Long term therapy centres around box rest initially, followed by controlled exercise over the following weeks and months to prevent the tendon contracting while it repairs itself. Your veterinary surgeon may wish to perform ultrasound examinations to visualise the extent of the injury and ensure that no further damage is being caused during the rehabilitation period. Although ultrasound exams do not aid the recovery of your horse they do allow the progress of your horse to be recorded and accurately assessed.
Immediate veterinary attention is essential to ensure the best prognosis and hence you should contact your veterinary surgeon as soon as you suspect a problem. A wait-and-see approach will worsen the chances of a return to soundness, or function.
Inflammation due to strain injury results in a distortion of the normal arrangement of collagen fibres within the tendon and in a deposition of scar tissue. These factors contribute to damaged tendons developing a bowed appearance. The extent of the changes may be subtle and although the fact that the tendon is bowed does not itself predispose the horse to further injury the sheer fact that the tendon has been injured previously means that the horse is at an increased risk of sustaining further damage.
Recent work at the Royal Veterinary College in London has investigated the properties of tendon and any predisposing factors. Generally speaking you cannot ‘train’ the tendons to become stronger i.e. the more exercise that is performed does not result in stronger tendons. In fact the opposite is true, tendons in fact became fatigued depending on the nature and intensity of the work that they have performed. Therefore to protect the tendons of your horse ensure that any strenuous work is performed on suitable ground.