The cavities of the head of the tibia for the reception of the condyles of the femur are much deepened, and exuberant nodules or vegetations of bone are thrown out around the circumference of this head. When we examine the femur, we find here also bony vegetations, arranged along the lateral margins of the con dyles, similar to those which we noticed around the corona of the head of the femur.* The part of this bone called the trochlea, upon which the patella moves, is also grooved verti cally, and the trochlea has rising edges to it, or crests, which will be found to correspond to the lateral margins of the patella when this bone is laid upon the trochlea of the femur. The anatomical characters of this disease when it has existed long, will of course be still more strongly marked. Ilowever, the dropsical effusion into the synovial sac will be found to be much less as the disease is of longer dura tion. The joint becomes more and more flexed, the tibia has a tendency to be partially dis placed outwards, and the toe is everted : the patella under such circumstances is dislocated on the external condyle, giving us another example of this luxation from disease. In the interior of the joint foreign bodies are found, while the articular and semilunar cartilages are altogether absorbed.
White swelling, or chronic strumous arthritis of the knee.—The knee-joint is more liable to the disease commonly called white swelling than any other articulation. This disease, though utterly insidious in its attack and slow in its progress, nevertheless presents some of the characters of an inflammatory complaint during its whole course. The first symptom generally is reported as a deep-seated dull heavy pain unattended by swelling and not increased by motion, but in children the swell ing is often the first symptom noticed. This is followed by pain, which, although it comes only occasionally, is severe, and is referred almost uniformly to the inside of the knee. Some increase of temperature of the affected joint on comparison with the other knee, can be ascertained.
The swelling does not at first encompass the whole joint, but first appears on the anterior and lower part of the knee, occupying in general the two little hollows on the different sides of the ligament which joins the patella to the tibia. This swelling is elastic, and on examination by the finger conveys a sense of softness and fluctuation, as if it contained a fluid, although no fluid to any amount wally exists. The skin over the knee becomes pale and shining, as if thinned. The subcutaneous veins dilate and become very evident. The muscles of the leg waste, so that the volume of this portion of the affected extremity is con siderably reduced, and the inferior part of the thigh just over the knee suffers a characteristic diminution in the measure of its circumference.
Patients under an incipient attack of white swelling first experience inconvenience in walk ing from weakness of the joint, a symptom which is more especially troublesome after exercise. But as soon as the pain becomes constant, the patient is no longer able to rest the weight of his body upon the affected limb without a great increase of uneasiness. On
this account he is willing to save the limb as much as possible; lie touches the ground, therefore, merely with his toes, trusting the support of his body chiefly to the other limb. In walking in this way the knee necessarily becomes bent, and what is thus begun becomes permanent from other causes; so that after a certain period the joint continues permanently in a state of flexion.
Although we occasionally see cases in which the leg remains extended on the thigh, they must be considered rare, for in general the leg is in a more or less forced state of flexion on the thigh, and such is the patient's apprehen sion of pain he will not on any account extend the leg voluntarily, nor allow it to be extended by others.
The earlier period of the disease is succeeded by a second stage,* in which the patient usually submits to the adoption of active and energetic treatment. The pain now not unfrequently diminishes, but the swelling continues in creasing, the ham becomes fully occupied by it, the extremities of the bones appear to enlarge, and become more prominent as the flexion increases. Attacks of inflammation • ensue, accompanied by pain starting up and down the limb, by which sleep is interrupted. These attacks are usually succeeded by effusion of fluid into the synovial sac of the joint and cellular interstices around : abscesses form, and some fluctuation may now be discovered in different parts of the swelling. If at this period, which may be called the third or sup purative stage of the disease, the bones be moved laterally, it will be perceived that the ligaments permit an unnatural degree of motion between them, and now, as in other articula ' tions, partial or complete luxation may occur. Such, however, is the breadth of the surfaces of contact of the bones of the knee-joint, that complete luxation seldom happens. The limb at this period is usually found lying powerless on its outer side and in the semiflexed position; and after some time a partial displacement of the leg outwards on the femur occurs : under other circumstances a partial or complete luxa tion backwards happens. Although the disease, arrived at this stage, seldom terminates favour ably, still instances do occur of unexpected improvement of the general health, the resolution of the swelling, of the absorption of matter, and of one of the forms of anchylosis taking place. But usually the matter formed in and around the joint goes on accumulating, the tension of the knee-joint increases, and now in most cases an accompanying of the foot is observed, a symptom than which there can be none more unfavourable. The nocturnal startings of the limb, disturbing the patient's rest, become more painful and urgent, and abscesses communicating with the interior of the articulation open externally by one or more orifices, and give exit to a quantity of matter, which rarely has the quality of laud able pus; on the contrary, it is for the most part a sero-purulent liquid, of a yellowish green colour, like whey, in which curdy mat ters are found floating. It is remarkable that little diminution in the size of the swelling follows the escape of this matter.