Cartilages are naturally divided into the true and the fibrous, and accordingly the morbid affections of each kind require to be separately noticed.

1. Deficiency And Excess Of Development

An absolute primordial deficiency of these structures is seen only in concurrence with the entire absence or partial development of organs, into the composition of which they enter.

So, too, an original excess of their development is very rarely met with, unless those parts, of which they form the ground-work, be more or less completely double. Now and then, however, some small supernumerary pieces of cartilage are observed on the external ear, the nose, and the larynx, and especially at the inlet of the last-mentioned part.

But during extra-uterine life, the production of cartilage is a less unusual occurrence. It approximates in the character of its texture sometimes to true cartilage, and sometimes to fibro-cartilage. Many of the false joints formed in cases of ununited fracture present instances of this growth in the white substance which invests the broken ends of the bone: cartilage is developed in many of the tendons, and in that situation it usually ossifies; the enchondroma, which is met with in the bones and different soft parts, affords another example of the same kind, etc. It is, however, necessary to remark, that many productions which have been hitherto reputed cartilaginous, or fibro-cartilaginous, are discovered by closer examination not to belong to either class: such, for instance, as the majority of the so-called loose cartilages in serous and synovial cavities, the cartilage found in encysted tumors, and in the parenchyma of organs, as the uterus or thyroid gland, and what are called cartilaginous transformations of serous membranes and of the inner coat of the vessels.

2. Deviations In Size

There appears to be no genuine hypertrophy of cartilages. Not unfrequently, indeed, they are found irregularly swollen in joints, in which fibroid growths hang from the synovial membrane, in which the articular ends of the bones are deformed by gout, etc.; but this is a consequence of disease of their texture, especially of their intercellular substance. The same diseased condition precedes their wearing down or atrophy, which is often found considerably advanced at the same time that this apparent hypertrophy exists elsewhere. Atrophy, like hypertrophy of the cartilage of joints, occurs only when there has been some previous disease of their texture: it chiefly affects the large articulations, selecting especially the hip and knee. The loss of substance goes on gradually, and quite independently of contact with purulent matter in the joint.

On opening such a joint one or more spots of various size are found at which some of the substance of the cartilage is lost. The margins of the defective spots are irregular, sinuous, and indented; the depth to which they reach varies, but they very commonly extend through the whole thickness of the cartilage. If any of it still remain, it is of a dull white color, and has lost its glistening and homogeneous appearance; it seems to have assumed a filamentous velvety texture, and is at the same time softer than natural, moist, and succulent. Not unfrequently it is covered over with a cellulo-gelatinous vascular substance. When the cartilage has been removed in its whole thickness, there is some variety in the state of the surface of the bone: it is sometimes, and no doubt always when first denuded, invested with a delicate cellulo-gelatinous organized substance, which fills up the aperture in the cartilage: at other times, especially at a later stage, it is covered with a white fibroid tissue, into which the organized substance just mentioned has been converted; in a third case, it may be literally laid bare, and it then has a smooth appearance, as if it had been polished; it is whiter than the adjoining part of the bone, and denser, as well as whiter than natural, to some depth from the surface.

The cartilages are very frequently found thus changed in some one part of a joint, when no alteration is perceptible in the texture of the other articular structures, or in the character of the synovial fluid. But when the cartilage is lost at several places, and the defective spots are more extensive and coalesce, various anomalies are noticed in the other articular structures, - anomalies which are compounded of those already depicted at pp. 139 and 159, as consecutive induration of the articular extremities of the bones, and a derangement of the joint, which is probably of gouty nature.

Attention has recently been attracted to this disease of articular cartilages, by the interest which the subject of diseases of joints has excited, especially in England, and more particularly with reference to their etiology and nosological import. In my own opinion, which is founded upon repeated investigations, the wasting of the cartilages is occasioned by some previous disorder in the cancellous structure of the articular ends of the bones, especially by their more or less intense inflammatory rarefaction, and consequent condensation. The first derangement of the texture of the cartilage is produced by the exudation effused into it from the adjoining bone. As the secondary process of induration goes on, the nutrient vascular apparatus of the spongy extremity of the bone becomes atrophied; and the further the induration advances, the more certain is the wasting of the previously diseased cartilage, for the extent and the degree of its atrophy correspond with the extent and intensity of the induration. The idea that this loss of substance arises from a true ulcerative destruction is altogether erroneous; neither at the spot itself, nor in the healthy condition of all the other articular structures, is there anything to countenance it.

In advanced cases, the cartilages may be entirely absorbed, or reduced to a few thin remnants, which are commonly situated at the borders of the articular surfaces. The opposite bones are thus brought into contact, and the ivory-like polish of their surfaces makes up, in some measure, for the loss of the cartilages. The disease is commonly known in Germany as the eburnated condition of joint, the name which was given to it by Lobstein. In its higher degrees it is associated with other anomalies, which have already been mentioned as occurring in the articulations, and which have yet to be collected and arranged together in the article on Diseases of Joints. It must be distinguished from other cases in which a similar, but much less marked ivory condensation and polish of the articular surfaces of the bones, succeeds to the destruction of the articular cartilages by ulceration, and in which, accordingly, the change in the spongy tissue of the bone is not the primary affection, but is due to the loss of the cartilage.

Atrophy of cartilage, and the change in the cancellous structure, which gives rise to it, are most frequently met with in advanced life. It is a remarkable fact, to which attention was first directed by Gulliver, that the disease is apt to occur symmetrically in corresponding joints.

The fibro-cartilages, which are most subject to atrophy, are those of the spine. They are found wasted in curvatures of the column, especially in considerable lateral curvatures; and so much of them may be absorbed in the concavities of the curves, that the bodies of the vertebrse come into immediate contact, and unite together. But, under other circumstances, they display a power of resistance, which surpasses that of the bones; and it is remarkable how little they yield to the pressure of aneurismal tumors. Moreover, in old age the intervertebral disks are subject to a form of atrophy, in which, first, the soft cartilaginous substance that enters into their composition is absorbed, and at a later period, their fibrous texture: they become dry and friable, their central gelatinous portion becomes fibrous, and partly disappears, leaving a cavity, which, as well as the peripheral parts of the disk, is filled with fat: the whole structure takes on a dirty yellowish, or rusty brown appearance, the fibres losing their lustre, and becoming dull.

3. Solutions Of Continuity

Lacerations of cartilages never occur without great external violence, and they rarely happen alone; either fractures of bone or lacerated wounds of soft parts being combined with them. Fractures of the costal cartilages are the most frequent; and either some ribs are broken at the same time, or the thoracic viscera are ruptured. Lacerations are met with also at the synchondroses of the spine and pelvis; and incomplete separations occasionally take place at some of the pelvic joints during difficult parturition.

These injuries are repaired in various ways. The uniting medium is never found to be new cartilaginous tissue. For the repair of injuries to true cartilages, the inflamed perichondrium supplies an areolar substance, somewhat like ligament, or else a bony callus. The tendency to reunite in the latter way seems to be regulated by the proneness of the cartilage to ossification when in its natural state. Thus fractures of the costal cartilages generally unite by means of a cup, or ring-shaped bony callus, which encloses the fractured part in a sort of capsule. Injuries to the fibro-cartilages heal like wounds of cellular tissue and tendons.