Synovial fluid

“ Lining the interior of the capsule, and all other parts of the joint cavity except where the articular cartilage is present, is the synovial membrane (fig. 4, dotted line) ; this is a layer of endothelial cells which secrete the synovial fluid to lubricate the interior of the joint by means of a small percentage of mucin, albumin and fatty matter which it contains.
A compound diarthrodial joint is one in which the joint cavity is divided partly or wholly into two by a meniscus or interarticular fibro-cartilage (fig. 5, Fc) . ”

“ If the illness has persisted for several days, however, the organism often can no longer be cultured from internal organs but may still be found in the joints. Under these conditions it is important to take several specimens of fluid and synovial tissue from as many synovial sacs of a joint as possible, because the organisms may be present in small numbers and limited to certain areas. ”

“ When this fluid is secreted in excessive quantities, it produces a disease known as "dropsy of the joints." There are numerous smaller sacs besides the synovial, called bursæ mucosæ, which in structure are analogous to them, and secrete a similar fluid. Some joints permit motion in every direction, as the shoulders, some in two directions only, as the elbows, while others do not admit of any movement. The bones, ligaments, cartilages, and synovial membrane, are supplied with nerves, arteries, and veins. ”

“ A very delicate connective tissue, called the synovial membrane, lines the capsules of the joints, and covers the ligaments connected with them. It secretes the synovia, or joint oil, a thick and glairy fluid, like the white of a raw egg, which thoroughly lubricates the inner surfaces of the joints. Thus the friction and heat developed by movement are reduced, and every part of a joint is enabled to act smoothly. ”

“ Usually they are present in large numbers, but sometimes there is only one, and it may attain considerable dimensions. They are not peculiar to joints, for they are met with in tendon sheaths and bursae, and their origin from synovial membrane may be accepted as proved. They occur in tuberculosis, arthritis deformans, and in Charcot's disease, and their presence is almost invariably associated with an effusion of fluid into the joint. ”

“ When, in spite of all the methods of treatment here described, the condition does not yield, very good results may be obtained by the aspiration of the fluid, and the injection of a few drams of a three per cent. or five per cent. solution of carbolic acid. This operation, though [Pg 88] simple, requires every aseptic precaution, and should never be performed in the presence of any acute symptoms.
For other phases of Synovitis see Arthritis.
ARTHRITIS
The structures of a joint are: bone, cartilage, ligaments, synovial membrane and, in some cases, fibrocartilage. ”

“ The tendinous synovial membranes, fine and delicate in the fœtus and in infancy, readily yield to the numerous motions which constantly succeed that age. More dense and compact in the adult, they become rigid in old age, exhale less fluid, are dry, and do not contribute a little, by the state in which they are, to the general slowness of the motions which that age brings with it. ”

“ The synovial membrane secretes a viscous fluid, which is called syn-o ́vi-a. This lubricating fluid of the joints enables the surfaces of the bones and tendons to move smoothly upon each other, thus diminishing the friction consequent on their action.
Observations. 1st. In this secretion is manifested the skill and omnipotence of the Great Architect; for no machine of human invention supplies to itself, by its own operations, the necessary lubricating fluid. But, in the animal frame, it is 50 supplied in proper quantities, and applied in the proper place, and at the proper time. ”

“ Synovitis.—When a joint has been injured, inflammation occurs in the damaged tissue; that is inevitable. But sometimes the attack of inflammation is so slight and transitory as to be scarcely noticeable. This is specially likely to occur if the joint-tissues were in a state of perfect nutrition at the time of the hurt. But if the individual or the joint were at that time in a state of imperfect nutrition, the effects are likely to be more serious. As a rule, it is the synovial membrane lining the fibrous capsule of the joint which first and chiefly suffers; the condition is termed synovitis. ”

“ If the synovitis or arthritis remains non-infected and the wound, traumatic or surgical, is not too large, healing by granulation occurs, and the discharge of synovia ceases. However, if synovial discharge persists too long because of tardy closure of an open joint, there is great danger of infection gaining entrance into the synovial cavity, or in some instances, desiccation of endothelial cells of the articulation occurs, in areas, and the reactionary inflammation eventually results in ankylosis. ”

“ Under judicious treatment the synovitis generally clears up, but it may linger on and cause the formation of adhesions which may temporarily stiffen the joint; or it may, especially in tuberculous, septic or pyæmic infections, involve the cartilages, ligaments and bones in such serious changes as to destroy the joint, and possibly call for resection or amputation.
The symptoms of synovitis include stiffness and tenderness in the joint. The patient notices that movements cause pain. Effusion of fluid takes place, and there is marked fullness in the neighbourhood. ”

“ It is different if the disease commence, as it sometimes does, in the human subject, in the cancelli of the bone, and on the attached surface of the cartilage, the free surface remaining some time entire and smooth. When the synovial membrane is primarily affected by chronic disease, the pain is in general trifling, often not complained of, and swelling of the part, from effusion, into the joint or neighbouring bursæ, first attracts attention, after it has existed, perhaps, in a slight degree, for a considerable time. ”

“ The joint lesions when they exist are very interesting. At the beginning all the periarticular tissues are infiltrated with a yellowish gelatinous serosity. The synovial membrane is covered with vascular aborisations of an extreme richness, which extend on to the articular cartilages. The synovial capsules are distended by a considerable quantity of thick synovia of a deep yellow or brownish tint, holding in suspension flakes of fibrous exudate more or less dense and abundant. ”

“ It is more dangerous than the inflammation of the synovial membranes in the form of bladders or bags, because the fibrous sheath which surrounds the inflamed membrane, not being able to stretch and yield to the swelling, like the cellular texture which surrounds the synovial bags, produces real strangulations, which it is often necessary to remove. I do not know whether the synovial texture of the tendons is exposed to the slow and tubercular inflammations, common to the articular serous and synovial systems. ”

“ The serous membranes are peculiarly liable to be attacked by secondary inflammation; and, when affected, suppurate with the greatest readiness. They generally exhibit but a slight degree of vascularity, and sometimes scarcely appear more injected than in their natural condition. In the peritoneal cavity, large quantities of unorganised lymph are frequently poured out, mixed with turbid serum or pus. The synovial membranes of joints, when affected, appear to run directly into suppuration, and will become distended with pus in a very short space of [Pg 55] time. ”

“ Joint lesions are comparatively common in #scarlet fever#, and were formerly described as scarlatinal rheumatism. The most frequent clinical type is that of a serous synovitis, occurring within a week or ten days from the onset of the fever. Its favourite seat is in the hand and wrist, the sheaths of the extensor tendons as well as the synovial membrane of the joints being involved. It does not tend to migrate to other joints, and rarely lasts longer than a few days. ”

“ An accidental wound of a joint, as from the blade of a knife, or a spike, entering the knee is a very serious affair, because of the risk of septic germs entering the synovial cavity either at the time of the injury or later. If the joint becomes thus infected there is great swelling of the part, with redness of the skin, and with the escape of blood-stained or purulent synovia. ”

“ The surface of the synovial layer is covered with minute processes or villi, which in diseased conditions may become hypertrophied. The synovia owes its lubricating property to mucin, derived from the solution of the endothelial cells on the free surface of the synovial layer. ”

“ In consequence of certain inflammations, this membrane acquires a thickness and opacity which enable us to distinguish it from all the neighbouring organs, from those even to which it adheres the most. 3d. The synovial bags are all as adherent as the articular synovial one, to the cartilages of their sheath and to this sheath itself; yet every one acknowledges their distinct existence. 4th. There are articulations with a fibrous capsule, in which the fibres are separated so as to leave a space between them through which the synovia would179 escape, if the synovial membrane did not line them. ”

“ Symptomatology.—No trouble is experienced in diagnosing distension of tendon sheaths, for the affection is very palpable. During acute inflammatory stages of this affection, some lameness is present—in infectious inflammation lameness is intense. Local heat and pain upon manipulation are readily discernible in all acute cases. And finally, where there is reason for doubt, an aseptic exploratory puncture of the wall of the fluctuating enlargement may be made with a suitable trocar, and the discharging synovia will be proof of the existence of synovial distension. ”

“ When the disease is confined to the synovial membrane, its onset is insidious, there is little or no pain, and no interference with any movement except complete extension. The chief evidence of disease is a white swelling on either side of and above the olecranon, obscuring the bony landmarks. ”

“ In the third, the fibrous tissue in the neighbourhood of a joint is primarily affected, the synovial membrane and cartilages not becoming involved till the disease is much advanced. It is not uncommon in the elbow of middle-aged persons who have been much exposed to the atmospherical vicissitudes, and is sometimes attributed to the effect of mercury or syphilis. ”

“ When the disease begins with swelling, which is of a chronic character, and produces but little inconvenience, and when the more urgent symptoms supervene after the swelling has continued for a considerable time, there is every reason to suppose that the disease has originated in the synovial membrane, or perhaps in the osseous cancelli, and this is generally met with in poorly fed and strumous subjects. ”

“ The temperature of the parts near the affected joints is higher than that of neighbouring regions. Sensibility is much more acute, and the slightest external pressure gives rise to pain.
In favourable cases the joint may appear scarcely injured. The principal symptoms are those of pain. In old-standing cases certain permanent changes may occur, such as thickening and hardening of the wall of the synovial capsule, fibrous infiltration of the tissues around the joint, or even diffuse and irregular calcareous infiltration. ”

“ In others, the joints, although stiff, can be moved but exhibit pronounced crackings. When there is much connective tissue formed in relation to the synovial membrane, the joint is swollen, and as the muscles waste above and below, the swelling is spindle-shaped. Subacute exacerbations occur from time to time, with fever and aggravation of the local symptoms and implication of other joints. After repeated recurrences, there is ankylosis with deformity, the patient becoming a helpless cripple. On account of the tendency to visceral complications, the tenure of life is uncertain. ”

“ Violent pain immediately occurs, and the patient is sick and faint. Discoloration and rapid swelling take place from extravasation of blood into the cellular tissue, into the sheaths of the tendons, and perhaps into the synovial pouches, in consequence of laceration of the bloodvessels. Effusion of serum and increased secretion of synovia afterwards occur, from incited action of the vessels. Thus the joint is deformed. Attentive examination is required to guard against mistakes ”

“ The ankylosing type of chronic arthritis is fortunately much rarer than those described above, and is chiefly met with in the joints of the fingers and toes and in those of the vertebral column. The synovial membrane proliferates, grows over the cartilage, and replaces it, and when two such articular surfaces are in contact they tend to adhere, thus obliterating the joint, cavity, and resulting in fibrous or bony ankylosis. ”

“ A small puncture which introduces into the synovial cavity infectious material of active virulence will cause an arthritis that is more serious, much more painful and more difficult to handle than is occasioned by a wound of moderate size, that affords ready escape of synovia even through the virulence of the infection be the same. ”

“ Violent inflammation soon commences, and can very seldom be kept within moderate bounds. Discharge of increased and vitiated synovial secretion takes place, followed by profuse and unhealthy suppuration. The cartilages ulcerate, and then the bones. The cellular tissue around becomes infiltrated, the parts swell and are discoloured, and collections of matter form probably at more points than one; perhaps there is a succession of abscesses. The condyles, and often a portion of the shaft of the bone, are denuded by the suppuration, and superficial necrosis results. ”