JOINT, in anatomy, an articulation or con nection between bones. Many of the im movable joints are so close in their union that the two bones practically become one, as in the dovetailed sutures of the skull. In the make-up of a movable joint there are the two hones, and covering the surface of each a layer of tissue of rubbery consistency called cartilage ; binding the bones together are firm inelastic bands of tissue called ligaments. Over the surface of the cartilage and the inner surfaces of the liga ments there is a thin, smooth layer of tissue, the synovial membrane, which is kept constantly moist with an oily fluid to prevent friction. Joints are classified according to the variety of motiqns they allow: the freest is the socket joint, as seen in the hip and shoulder.
Diseases of Joint-diseases are dis tinguished by names that indicate the principal structure involved and the causes of disease. Where the cause is a specific disorder, as tuber culosis, rheumatism, syphilis or gonorrhoea, the name of that particular malady is given to the inflammation. The only structure of a joint that is apt to be involved alone is the synovial mem brane, and inflammation of this structure is called synovitis. Inflammation of all the joint structures is called arthritis, and where the bone is the primary seat of the trouble, or is prin cipally involved, the name osteo-arthritis is used.
This condition results from in juries (sprains, bruises and wounds), from overuse, acting as an injury, and from poisons circulating in the blood. The joint is painful, moves with greater pain and may be red outside. Blood-serum is poured out and the synovial sac is distended. (This condition constitutes °water on the knee”. The general symptoms and severity depend on the cause of the trouble. Ab solute rest of the joint and pressure by a snug bandage hasten recovery. When such injuries are repeated, or when the inflammation is slight but persistent, painting with iodine tincture may be of value. When the condition of inflamma tion reaches the suppurative stage all the struc tures of the joint are involved and the condition is considered under the term Arthritis is due to the extension of disease of contiguous bone, or it may result from wounds or in the course of various diseases. The joint becomes swollen, red, very painful and the general symptoms are severe. When the poison is sufficiently virulent, suppurative arthritis results and the pus col lects in the synovial sac. (See INFLAMMATION). In this condition the joint becomes aboggy,E and the poisoning of the entire system is so severe as to warrant the most radical measures for relief. Opening the joint and allowing the es
cape of the pus, with thorough cleansing, may be sufficient, or the limb may have to be sacri ficed. See ARTHRITIS ; ARTHRITIS DEFORMANS ; GOUT ; RHEUMATISM ; SYPHILIS.
This is a deformity of the legs, consisting in the angular projection of the knee inward, and is sometimes called in-knee. It arises in children learning to walk who are affected with rickets (q.v.). The deformity is due to the faulty growth of the bones which enter into the joint. In early life, correction of it may be secured by splints and braces; but when the bones become less pliable, the femur, the tibia, or both, may have to be severed by chiseling and the bones held in the normal line by plaster casts until union has taken place.
Charcot's The peculiar form of arthritis thus named occurs in the course of locomotor ataxia, the knee-joint usually being the one affected. The joint swells painlessly, the structures are worn away and the function of the joint is lost.
These are wrenches resulting in more or less stretching or laceration of liga ments, hemorrhage in and around the joint and sometimes the displacement of tendons. The part usually swells at once and movement causes severe pain. This injury may closely re semble a joint-fracture. Absolute rest of the joint must be insisted upon, as synovitis may follow. Alternating hot and cold applications, if started early, lessen the damage. The joint should then be snugly bandaged and kept so until swelling and tenderness disappear.
Wounds of Injuries of this nature may cause damage directly to the structures or by infecting the joint and producing arthritis. Penetration into the synovial sac is indicated by an escape of the viscid fluid.
Floating These are rarely seen except in the knee-joint, where they are ordi narily due to a small portion of cartilage being bitten off between the bones; this piece then floats around in the synovial sac and causes trouble when the bones lock together on it. When this occurs, the patient falls to the ground because of the severe pain. The synovial mem brane is injured and is apt to be mildly in flamed. These bodies may sometimes be felt through the skin and can be held, by holding the joint in the same position, until an opening is made; but ordinarily when the attacks become so frequent as to be unbearable the joint has to be opened and searched.