Tendons attach muscles to bones and in comparison to muscles are relatively inelastic. The evolution of the horse has resulted in an animal that stands on its toes. The bellies of the muscles that flex the lower joints of the legs are confined to the upper limbs that is above the knee or hock, the superficial and deep digital flexor tendons are long flattened cords of tissue, approximately oval on cross section, which connect these muscles to the middle(second) and distal(third) phalanges(short pastern bone and coffin bone)  These tendons are only covered by skin and are there fore extremely susceptible to damage by a direct injury to the lower leg.

There are a few types of tendon injury and they vary in the severity and the long term consequences for the horse.

Constriction of the tendon by an over tight bandage causes the classical `bandage bow`-localized inflammation around and within the superficial digital flexor tendon inflammation results in the accumulation of fluid causing swelling and distortion of the normal anatomical arrangement of fibrils within the tendon. Usually the fibrils are not themselves damaged, so the long term consequences for the horse are not to serious, although a small swelling often persists at the site of the injury.

A direct blow to the tendon is more serious because although it is a localized injury, there is usually a rupture of some of the fibrils and bleeding into the tendon, the fibrils will be filled with mechanically inferior collagen, so there will be more likely hood of more injury, though the prognosis is more favourable for this type of injury than tendon strain.

In a strained tendon the normal pattern of fibrils and fibres is disturbed and some of the fibrils rupture. In more serious cases fibres or complete fascicles of fibres may be damaged. Occasionally the entire tendon is completely separated, there is bleeding into the tendon and accumulation of inflammatory fluid, which contains enzymes which may cause further damage to the collagen fibrils.

Tendon strain in the forelimbs is much more often found than those in the hind legs. The forelegs the superficial digital flexor tendon is more frequently injured than the deep digital flexor tendon. The most common site of injury is the middle of the super flexor tendon , at this point the tendon has most stress put on it, back at the knee conformation hyperextension of the fetlock associated with long sloping pasterns predispose to injury.

Tendon strain is definitely a hazard of riding at speed, especially jumping as does traveling at speed on uneven ground.

There will be considerable pain and swelling on onset of the strain, when the initial swelling has subsided it is very difficult to assess the extent of the damage therefore veterinary advice should be sort as soon as possible to obtain an accurate prognosis as it is important to differentiate between minor tendon strain and damage to localized trauma, sometimes tendon damage can present without lameness in the early stages the amount of swelling may be slight, usually the vein on the inside of the leg is enlarged a few days rest and cold applications seem to resolve the problem but when put back to work the strain returns and deteriorates

These early signs must not be ignored as serious damage can be done. It must be remembered that tendon strains often do not cause lameness unless severe, therefore small swellings should not be ignored just because the horse seems to be sound.

Treatment of acute injury.

Treatment of acute tendon injury is to reduce swelling as soon as possible to restore the normal alignment of the tendon fibrils and to relieve pain, movement should be limited, cold compresses, ice packs bandages to the legs reapplied at frequent intervals, pain relief

must also be given the quicker the soft-tissue swelling is down the more likely hood of a good result. horses become sound long before repair of the damaged tissue is sufficient to withstand the stresses of normal work, so the temptation to return to work early must be resisted.

Tendon lacerations

Lacerations can completely sever the superficial digital flexor tendon and the deep digital flexor tendon and are serious injuries

the wound must be cleaned and the badly damaged tissue removed this is done under a general anaesthesia and the tendon if severed

can be stitched back together provided that the ends are not too widely separated, the limb will have to be encased in a plaster

cast usually the heel is raised so as not to pull the tendon ends apart, then the height of the heel is gradually reduced

to avoid excessive contraction of the tendon during healing.

Displacement of the superficial digital flexor tendon of the hind limb,

The superficial digital flexor is a flattened fibrous band that passes over the point of the hock, two fibrous bands detach on either

side and insert on the calcaneus and help to keep the tendon in position, if either or both of these bands are damaged the tendon

may be displaced the injury usually occurs at speed, the tendon might move off -on the hock the horse shows great distress

and is unwilling to put weight on the leg, initially there is minimal soft tissue swelling and careful palpation reveals the injury

within 24hrs there is considerable swelling making palpation of the limb difficult.

If the tendon is displaced and remains displaced a prolonged period of rest will show improvement, some horses are able to work

although there maybe some mechanical impairment of the gait.

Curb

Sprain of the tarsal ligament results in a swelling usually at its insertion on the lower part of the hock this swelling must be differentiated

from the head of the fourth metatarsal bone which can be very prominent. Strain of the ligament may cause mild lameness.