CHAPTER VIII.

DISLOCATIONS OF THE KNEE AND ITS CARTILAGES.

DISLOCATIONS OF THE KNEE.

TRAUMATIC dislocation of the knee-joint is very rare, as might be expected. from a consideration of the size of the joint and the strength of the ligaments concerned. Severe violence is required to produce dislocation, and hence these injuries are usually either compound or complicated by fracture of the bones in the immediate neighbourhood.

VARIETIES.-The knee may be dislocated forwards, backwards, or to one side, and the dislocation may be complete or incomplete; usually it is incomplete.

Dislocation of the Tibia forwards.-This may occur from direct violence, such as a severe blow upon the front of the femoral condyles when the limb is fully extended; the lower end of the femur is driven directly backwards. Generally, however, the accident occurs from indirect violence, as when the foot becomes caught in a hole and fixed, whilst the weight of the body carries the upper end of the femur forward, and thrusts the lower end forcibly backwards against the posterior ligament of the knee-joint, which gives way. The other ligaments of the joint are also ruptured to some extent. The popliteal vessels and nerves generally lie in the inter-condyloid notch of the femur and are pressed upon; should the artery be atheromatous it may be torn across. This is the most common form of dislocation.

Dislocation of the Tibia backwards, although common as a result of disease, is rarely of traumatic origin. It may result from violence applied either to the head of the tibia in front or to the lower end of the femur behind, the knee being in a flexed position at the time the injury is received.

Lateral dislocations of the knee are still rarer, outward dislocation being perhaps more frequent than the inward form. They are almost always incomplete.

TREATMENT.-As these dislocations are generally partial, reduction, as a rule, is readily carried out. The patient is anæsthetised, and the lower end of the femur is fixed by an assistant, whilst the surgeon makes traction on the leg and employs the movements necessary for the reduction of the dislocation. Thus, in dislocation of the tibia forwards, reduction is effected by traction followed by flexion of the knee. When the tibia is dislocated backwards, traction is also employed, and the head of the bone is pushed forwards into position. In lateral dislocations, traction alone may suffice, but if necessary lateral pressure may be made upon the tibia.

After-treatment. The principal difficulty lies in the after-effects of the injury. Extensive damage is done to the joint, accompanied by considerable effusion of blood, and this is followed by a sharp attack of synovitis. Union of the ruptured ligaments must be aimed at, otherwise a permanently weak joint will be left. The limb should be put on a straight splint, and an ice-bag or Leiter's tubes (see Vol. I. p. 10) applied to diminish the effusion. Passive movement should be begun during the second week, generally under an anæsthetic at first, as the internal damage is considerable and movement will cause great pain. A firm leather splint may be moulded to the joint three weeks after the accident, and the patient allowed to get about. The splint is removed two or three times a day for movements and massage. As a rule it is necessary to wear a lace-up knee-cap for several months.

DISPLACEMENT OF THE SEMILUNAR CARTILAGES.

Either of the semilunar cartilages of the knee may be injured, generally as the result of some sudden strain, more particularly a twist of the leg on the thigh, such as occurs in playing football, lawn tennis, or any movement in which the leg is firmly fixed on the ground, while the body is twisted violently. The internal cartilage is much more often injured than the external.

The result is that sudden, and often excruciating, pain is felt in the joint, the patient may fall down and is frequently unable to straighten the limb for a time. In some cases a prominence, in others a depression, may be felt in the situation of the semilunar cartilage, and in some cases the patient may not be able to straighten the knee completely for some weeks. The injury is frequently followed by synovitis which may last for some days or even weeks. Not uncommonly the patient has further accidents of the same kind, the fact being that in many cases the injured cartilage does not recover completely, and, being more or less loose, moves in the joint and becomes caught between the tibia and the femur from time to time. It is important to note that the dislocation of the internal semilunar cartilage follows outward rotation of the tibia on the femur, while in the case of the external cartilage, the rotation is inwards. The lesions in the cartilage are of various kinds; sometimes it is split

more or less longitudinally, in other cases it is divided transversely. In some cases the main portion of the cartilage is torn from its connection with the tibia, but remains attached to the spine of the tibia at both ends. In others, one of the ends attached to the spine of the tibia is torn through and the free part curls up in the inter-condyloid notch and becomes nipped between the ends of the bone. The exact lesion of the cartilage, however, cannot be clearly made out until the joint is opened.

FIG. 37.-INJURIES TO THE SEMILUNAR CARTILAGES. The sketches show the usual types of injury to the semilunar cartilages. In A the anterior end is torn away from its attachment; in B the cartilage is torn nearly across about its middle; in C the periphery is torn loose from the head of the tibia; in D there is a longitudinal rent in the cartilage.

TREATMENT.-It is well to consider the treatment under two headings cases that are seen immediately after the occurrence of the first injury; and cases in which the trouble is constantly recurring.

In cases seen immediately after the injury, the first thing to do is to try to reduce the displaced cartilage. This can be accomplished by flexing the joint completely in order to disengage the cartilage from between the condyles, and then, while keeping up pressure over the side of the articulation, suddenly extending the leg, at the same time rotating the foot inwards (if the internal cartilage has been damaged), or outwards (if it is the external which is at fault). This manipulation should be repeated several times until the joint moves smoothly and there is no

obstacle to complete extension. After the cartilage has been replaced, it is well to put on a posterior splint for two or three days, and apply cold so as to diminish the effusion into the joint. After that time the splint should be left off and massage and passive movement should be employed daily for about half an hour at a time. After the effusion has disappeared, the massage may be limited to the muscles of the thigh, the object being to keep up the tone of the muscles, and prevent the atrophy which might otherwise occur; it should be continued for about six weeks. As soon as the swelling has disappeared, the patient may be allowed to walk about, but only to a moderate extent, and it is well to strap the joint for a few days.

In recurring cases, the displacement often takes place after the most trivial injury. The patient is in constant danger of falling, whilst the usefulness of the limb is much diminished, and there are frequent attacks of synovitis, for which he has to lie up. Under such circumstances there is little chance of curing the trouble in any other way than by operation. If, however, the patient declines to have an operation performed, an attempt must be made to replace the cartilage by the manipulations previously described. He should also be told to keep his knee more or less stiff when walking, and when the internal semilunar cartilage is at fault, he should remember to keep his toes well turned in. Massage to the muscles of the thigh must be employed, while active movements against resistance should be carried out.

FIG. 38.-INCISION KOR REMOVAL OF THE INTERNAL SEMILUNAR CARTILAGE. The thick line indicates the incision marking out the skin flap, the dotted one, that through the capsule of the joint.

The object of the treatment is to strengthen the muscles of the thigh, so that they may hold the limb firmly and prevent the leg being everted. Splints do not seem to be of any particular value, the objections to them being that they are very uncertain as regards keeping the cartilage in its place, and that their use leads to atrophy of the muscles, and so prevents the limb regaining its strength.

Operative measures.-Operation is practically devoid of danger if carried out with careful antiseptic precautions, and the results obtained by it are excellent. It should not be undertaken, however, unless the surgeon is sure of keeping the wound aseptic. In the case of the internal cartilage an incision with its convexity forwards is made over the inner aspect of the knee commencing on the inner side of the joint about half an inch below the articular surface of the tibia and running upwards along the inner side of the patella (see Fig. 38). A flap of skin is

raised and turned

backwards, so as to expose the front and inner part of the joint. The capsule is then incised horizontally about a quarter of an inch above the edge of the tibia, combined, if necessary, with a vertical incision at the anterior end. The joint cavity is then freely opened and the cartilage inspected. In all cases it is well to remove the cartilage as completely as possible; attempts to stitch it to the lateral ligament or to close any rents in it, are practically failures. In order to gain good access the knee should be flexed so as to increase the aperture in the capsule; the anterior end of the cartilage should be seized and pulled forwards forcibly while its attachments to the tibia are divided with a few touches of the knife. A tenotomy knife is then introduced as near as possible to the posterior attachment, which is divided and the cartilage removed. In some cases it is very difficult to get quite to the back of the joint, but when the cartilage is firmly attached there, no trouble seems to result from leaving a small portion behind. All bleeding points are now tied, any blood-clots washed out of the joint by sterilised saline solution and the incision in the synovial membrane closed with catgut stitches. It is well to leave a little interval between the stitches, so that any fluid that forms in the joint may escape into the cellular tissue, and thus be more readily absorbed. The fibrous capsule is next sewn up and the wound closed, antiseptic dressings applied, and the limb placed upon a pillow. No splint is necessary and the patient may move the joint in bed from the first. In about a week the stitches may be taken out and active and passive movements should be begun, and gradually increased in range. Massage should also be carried out, especially over the muscles of the thigh, and about ten days after the operation, if there be no marked effusion into the joint, the patient may begin to walk. For the first week or two it is well to support the joint by an elastic bandage applied over a mass of wool in order to prevent synovial effusion.