Most of the painful knee conditions of which patients complain are not directly due to true pathological conditions either of the knee joint itself or of its neighboring structures, but rather to affections of other portions of the leg that set a special strain upon the knee and, above all, to various kinds of foot disturbances. The erect position is maintained principally by a nice balance of nervous and muscular energy in the knee joint and its surrounding structures. Any irregular sensory or motor impulses to the knee-joint or to the muscles of the thigh will disturb the absolute equilibrium of the flexors and extensors and will make standing painful or even impossible. Whenever a morbid condition requires a different use of the muscles and tendons around the knee from that to which they are accustomed, fatigue readily ensues, and aches and even tenderness in muscles and tendons develop as the result of the over-exertion. These collateral conditions must not be overlooked in the diagnosis and treatment of painful knee conditions.

Etiological Factors.—Even a slight sore on one foot will give rise to considerable achy fatigue of the knee of the opposite leg, because, consciously or unconsciously, we stand much more on that leg, use it more in walking, and spare the other because of the pain induced by use of the foot. Above all, throwing more weight on the other leg causes us to use muscles a little abnormally with consequent soreness. This painful fatigue is most likely to be felt around the knee, though it may extend to the hip and even the lumbar {410} region of the well side if the foot continues to be spared for a number of days. Particularly will this be true if there is anything the matter with the big toe, on which so much of the use of the foot depends. An ingrowing toenail will not infrequently give so much discomfort to the well knee and hip as to make the patient sure that there must be some rheumatic or other condition at work in these joints. The serious affection of the joint which the patient apprehends is found to be no more than a sympathetic fatigue induced by having to use his feet, or one of them, a little differently from usual, perhaps because of some condition that leads him to spare them. To call the patient's attention to this is of itself therapeutic.

Inequality of Legs.—The effort required for standing and the accurate balance of the muscles involved in it is such that any mechanical disturbance of the feet or legs or even a trivial pathological condition causes painful fatigue. It must not be forgotten, for instance, that the presumption that human limbs are of exactly the same length is not confirmed by accurate measurements. There is an average difference of probably half an inch in length between the limbs of normal persons, and there may be even a difference of more than an inch before deformity is said to be present. The longer limbs are likely to do more work and are, therefore, more subject to fatigue and consequent complaint. One of the reasons why we can distinguish persons by their gait even at a distance is that the difference in the length of their limbs makes noteworthy characteristics in their walk.

High Heels.—People who are used to walking in a natural manner and who don a pair of high-heeled shoes for the first time are sure to complain of pain in the calf and knee, because the high heels require them to hold the knee more rigid and in a somewhat different position from that required when the persons stand under ordinary circumstances. It is the unusual in muscular effort that gives rise to the extreme fatigue which becomes positive pain if it is allowed to continue. It is curious how small a raising of the heel will cause discomfort. Over and over again I have known the careless putting on of rubber heels to be responsible for pains around the knee, which in damp weather were the source of so much discomfort that it was hard to persuade the patient that he was not suffering from rheumatism or some serious incipient pathological condition.

Unusual Occupations.—Joint pains often develop after the patient has been doing something quite unusual and putting an unaccustomed strain upon his muscles. I have often seen dispensary patients whose knee pains began after there had been a family moving. In the course of the removal of household goods, both men and women are likely to help in hanging pictures, in taking them down, in moving heavy furniture and other occupations of this kind which make them extremely tired. If there is any tendency to relaxation of joint structures the tiredness may manifest itself as a sense of painful discomfort. The knees are particularly likely to suffer if there is a relaxed condition anywhere in the leg. It must be remembered that the laxity of tissue which predisposes a patient to weak or flat feet will have a tendency to produce some looseness of fiber, at least, also in the tissues around the knee. The patient may not have a wabbling knee, nor may he be able to overextend the limb, but still there will usually be some noticeable relaxation of the tissues which will help in the production of the painful condition by {411} making exaggerated calls upon the muscles in order to keep the joint in proper position in spite of the over motion in it.

The disturbance is most frequent in waiters, store clerks, tailors' cutters and fitters, bench men in the trades, and in all those who have to spend much time on their feet. I have seen many such ready to give up their occupations, though they had no other resource and the future looked very blank, indeed, away from their work. It was difficult at first to persuade them that a slight yielding of the arch had so changed mechanical conditions in the use of the muscles of the leg as to produce such pains. But as soon as they were put in a condition where their arch was not allowed to sink, they were at once relieved of their discomfort to a great extent. The question of treatment is discussed more fully in the chapter which follows on Foot Troubles.

An interesting set of painful conditions around the knee develops in a class of people in whom it might least be suspected of being due to over-exertion connected with their occupations. These are lecturers, clergymen, teachers, and others who, for several hours each day, are on their feet in a position from which, as a rule, they do not move, but stand almost perfectly quiet. A distinguished laryngologist has pointed out that not infrequently men who come to be treated for the chronic laryngitis, which is known as clergymen's sore throat, but which is seen so frequently in those who have to talk in the open air, auctioneers, cart-tail orators about election time, and in lecturers to large audiences who do not know how to use the voice, also complain of grievous discomfort from painful knee conditions which often makes the ascent or descent of stairs a painful task. He attributes the simultaneous occurrence of these conditions to some blood dyscrasia, uric acid, or the like, affecting the two most used sets of muscles and organs, the legs and the vocal cords. Whenever I have seen this condition—and circumstances have brought me into intimate personal relations with many clergymen and lecturers—the trouble at the knee has been due to some yielding of the plantar arch, while the laryngeal condition, if present, was due to an erroneous mode of using the voice consequent upon lack of proper training.

Sufferers of this kind must be warned not to stand absolutely immovable while addressing an audience. Some men stand without moving during a whole hour's lecture. This is unfortunate, for it obstructs the return circulation through the tense muscles, for the venous circulation was intended to be helped by muscular contraction. Many a man finds, as he comes down from pulpit or platform, that his knees are stiff and sore, though a moment before he knew nothing about it. The failure to notice any discomfort before is of itself an example of the influence of the mind over the body for the relief of pain.

Associated Lumbar Discomfort.—The painful condition around the knee which develops when high heels are worn is almost sure to be accompanied by pains, or at least a tired feeling, in the back. If we convince the patient that the trouble is due merely to a derangement of the mechanism involved in maintaining the erect posture we shall have scant need of medicine or even of local treatment. But as the pain is much worse on rainy days, owing to the relaxation of the muscles, we must be careful to remove the patient's suspicion that the pain must have a rheumatic origin. The restoration of normal mechanical conditions with the removal of the cause will prevent the {412} recurrence of the affection, and if some discomfort remains, the patient will not worry, and the muscles will gradually grow accustomed to the strain upon them. Of course, these conditions of discomfort are more common in those who are not naturally strong, who are run down, who are under-weight, or whose neurotic tendency will make any irritation seem worse than it is.

Heavy and Light Patients.—Two classes are likely to suffer more than others from these conditions. They are the people who are overweight and the people who are underweight. Those who are overweight exert much more effort to maintain the erect posture than ordinary people, and, besides, in most adipose persons the distribution of weight is such that a disproportionate amount of it is carried forward of the normal center of gravity. High heels cause a further tilting forward that has to be counter-balanced, and that, at least at the beginning, gives rise to muscular discomfort. In people who are underweight the nutrition of the muscles has suffered, and, as a consequence, they are not able to support the frame as well as before. In them the additional effort necessitated by the tilting tendency of high heels is particularly felt because such people are nearly always among the neurotically inclined.

Muscle Disuse.—Sometimes treatment of these conditions seems to lead up to the disuse of certain muscles and the over-use of others. I followed for several years an interesting case of this kind in which the course of the affection was so typical as to deserve to be recalled. A fuller account of the case occurs in my paper on "Rheumatism versus Muscular and Joint Pains" in The American Journal of the Medical Sciences, August, 1903.

In that case the joint symptoms caused by the pinching of a loose cartilage within the joint occurred suddenly on two or three occasions, so that a surgeon deemed it wise to put the knee in plaster. As a consequence, some atrophy of the muscles of the leg occurred, and a halt became habitual in the gait. Through this halting gait, the muscles of the back on the same side were also spared and thus became somewhat atrophied. Painful conditions developed in the muscles of the other side of the back from the over-use necessary to compensate for the condition on the less-used side. All of the muscles on the affected side became painful, apparently because of the atrophic condition to which they were reduced.

The young man, though with the best of good will, was utterly unable to conquer the tendency to halt in his gait, and so the muscles remained under-exercised and were used at a mechanical disadvantage, with the usual painful result. He went to at least two prominent orthopedic surgeons, who assured him that all he needed was confidence in himself to walk straight, and that then the normal condition of the muscles and absence of pain would result. But their directions were absolutely without result. He went through the hands of masseurs, of osteopaths, of rubbing quacks of all kinds, and suffered at least two attacks of artificial eczema as a consequence of the use of turpentine liniments, but he remained after it all in what he considered to be an intensely miserable condition. These cases are practically always cured by definite exercise of the muscles of the affected limb so as to bring them back to their normal tone. It requires special attention for this purpose, however, and the patient's mind must be brought to understand that at first the unaccustomed use of muscles will cause discomfort, but that this will disappear after a time. These patients are persuaded that they must be "cured" to get well.{413}