It is convenient to consider sports injuries in two main groups:
(1) Minor injuries, in which there is no real damage to the tissues, such as strains of muscles and tendons; The reactions of the tissues to trivial injuries are often obscure and difficult to assess; in general they are those of a mild, localized inflammation, and pain and stiffness are the main symptoms. Many of the injuries are caused by over-use of the affected part, and clear up with rest; some require support by strapping or bandaging, especially when training is resumed. If more specific treatment is necessary it follows the lines suggested for the more serious injuries.
(2) More serious injuries, in which there is actual destruction of some of the tissues, such as muscle tears and sprains of ligaments. Three main changes occur in the tissues when they are more seriously injured: loss of substance or continuity, rupturing of some of the small blood vessels and localized inflammation.
When some part of a structure is torn or crushed (as by a blow), the small blood vessels of the injured area are ruptured, and bleed into the tissues. The blood seeps between the various tissue layers; its spread is aided by the action of the muscles, the effect of gravity, and the pressure of the membranous coverings. This is the reason why braising often appears in areas which are some distance from the injured part. Soon after the injury the capillaries constrict and the blood clots. The blood then consists of a jelly-like substance and a fluid part (the plasma, which has lost certain elements concerned in the clotting process). The clot seals off the ends of the ruptured vessels, and links the torn tissue fibers together. Special connective tissue cells, known as fibroblasts, grow into the links and eventually repair the damage. The fluid part of the escaped blood is drained away by the lymphatics, and eventually returns to the general circulation.
At the same time as these changes occur the undamaged capillaries in the neighborhood of the injury dilate, so that they hold more blood than usual. Their walls become more porous, and a considerable amount of sticky blood fluid (plasma) and a large number of white corpuscles pass through them into the tissues to mingle with the blood from the damaged vessels. The free blood fluid is known as inflammatory exudates.
These changes are concerned with repair and healing. The inflammatory exudates stimulate the formation and growth of the fibroblast repair cells. The white corpuscles act as scavengers and remove the tissue cells which have been destroyed; they also deal with the blood clot in the same way. The signs of these changes are local heat, redness, swelling and pain. The heat and redness are caused by the extra amount of blood in the arterioles and capillaries of the injured area. The swelling is due partly to the dilation of the capillaries and partly to the accumulation of fluid in the tissues. The pain is either the result of some of the nerves being involved in the injury or of their being compressed by the distended tissues.
