The knee is said to be "broken" when the skin is cut partially or completely through. In the former case it may be of little moment, but in the latter it is always more or less serious, for in addition to the skin, important structures beneath may suffer more or less injury at the same time. The sheaths of the tendons may be opened, the tendons themselves may be lacerated or even divided, the bones may be bruised, or the joint may be contused and punctured.
Forcible contact with the ground as the result of stumbling is the immediate cause of broken knee. Horses stumble for many and various reasons. Of these, some have reference to conformation and condition, others to weakness, want of energy, or disease, while not a few are the outcome of bad shoeing and neglected feet. Horses with upright pasterns whose toes are turned out, and others with narrow chests whose action is close, are more or less addicted to stumbling, as are also animals with heavy heads and fleshy, ill-carried necks. Want of condition and a natural deficiency of nervous energy likewise conduce to it. Diseases of the feet, especially navicular disease and corns, are often the precursors of broken knees. Animals addicted to brushing or speedy cutting are also rendered liable to fall. Disproportion in the thickness of the shoes, as when they are unduly high at the heel or the toe, may also lead to stumbling.
A broken knee is a very patent defect, but the severity and serious nature of the injury can only be determined by a careful examination of the injured part. The skin may not be completely divided, although the wound is considerable in extent. The lesion, on the other hand, may be comparatively small, but may extend deep down towards or into the joint. In other instances the joint escapes injury altogether, but the tendons beneath the skin are seriously contused and torn, and their sheaths are laid open.
The amount of lameness present will, of course, depend upon the extent of the injury and the structures involved. A mere skin wound rarely occasions more than a slight stiffness, but any implication of the joint is attended with great pain and disablement, as well as a good deal of general systemic disturbance, and in a less degree the same may be said of injuries affecting the tendons. In injuries to the joint the leg is rested on the toe, and the animal declines to impose weight on the affected limb. Passive movement of the knee occasions considerable pain, and should the joint be opened the wound discharges a yellowish, transparent, glairy fluid, which later on coagulates over the orifice in the joint into a soft jelly-like substance. A considerable amount of swelling invariably results when the articulation is injured, and the patient seldom escapes without more or less permanent enlargement or stiffness of the injured joint.
A clean stable is the first requirement of animals suffering from wounds. This provided, the part must be thoroughly cleansed from all dirt by means of warm carbolized water. It should then be carefully probed to determine its depth and the structures injured, and to discover and remove any grit or other foreign matter that may exist in it. Should it be found that the joint is implicated, the patient should be put into slings. The wound should then be prepared and freely dressed with a solution of carbolic acid and covered with a thick pad of absorbent wool, and secured by a clean flannel bandage. Both the wool and the bandage should be well baked before being used. The dressing will require to be renewed morning and evening for the first two days. Afterwards the renewal will only require to be made once daily. The patient should receive a mild dose of physic, and be placed on a light diet, including a liberal allowance of green meat or roots.
If the tendons are torn, as they sometimes are, the loose shreds must be carefully removed close up to the body of the tendon by means of suitable scissors. In slighter injuries of the knee the horse may be put on the pillar reins, and prevented from lying down, while the wounds are dressed as prescribed.
When bruising of the parts is very extensive and swelling considerable, bandages well wrung out in hot water may be applied over the dressing for two or three hours after the accident, and repeated if necessary. Where the wound in the knee has been considerable, the parts should be allowed to undergo complete repair before the patient is allowed to lie down, or the uniting structures may be forced apart, and the wound again laid open.