The adductors and abductors of the hip also rarely require individual muscle training, though they frequently call for strengthening by exercises. The first step in muscle training, namely, teaching whichever happens to be the stronger to relax with gravity to aid it, can, in the case of the abductors, only be accomplished with the patient on his side by means, as a rule, of assistive abduction. Training, therefore, should begin with the patient recumbent, the weight of the whole limb being supported by a cord that passes to a support placed under the heel. The knee, of course, is in full extension. By moving the point of suspension beyond the middle line to the other side of the body we give assistance to adduction. By moving it away from the mid-line in the opposite direction we increase resistance to adduction. In this way the work done by the adductors can be varied from negative, past zero, to a very considerable positive amount. When standing, with the cord of the weight and pulley attached to the inner side of the foot, adduction can be assisted, but it is not necessary, as gravity is all-sufficient. So much so is this true that even if the cord is attached to the outer side of the foot adduction (from a position of abduction) is only an assistive exercise until a considerable weight has been attached. Exercises in the high-stride-sitting position are, of course, invaluable at a later stage. The rest position of the adductors is, of course, attained whenever the knees are in contact with one another, The patient should be instructed constantly through the day to brace his knees firmly together.

Flexion and extension of the knee are the property of the hamstrings and the quadriceps. If the training of the latter is considered in detail the reverse process will be that applicable to the hamstrings. The maximum assistance to the quadriceps from gravity (and therefore resistance to the hamstrings) is secured while the patient is prone, moving the leg from the vertical to full extension. Lying on the side (see Fig. 48, p. 92) we reach the dead point, and then we aim so to arrange the action of gravity that resistance is added by slow stages. This apparently difficult problem is open to the easiest possible solution. The patient, with head and shoulders supported, lies recumbent on a couch. First the heel, too, rests upon it, and the patient is taught to dorsi-flex his foot to the fullest extent and then to drive the back of the knee down on to the couch. When he can do this he shifts down towards the end of the couch so that the heel alone is unsupported by it. Again the knee is pressed down till in contact as before. By slow stages (usually about six) he shifts his position further and further towards the foot of the couch until, finally, its edge rests under and supports the back of the thigh, the leg, when all muscles are relaxed, hanging vertically downwards. When the flexion of the knee reaches an angle of about 45° the patient will find it easier to assume a sitting attitude in place of the lying or half-lying. The use of apparatus in training the quadriceps is very varied, as it may be used lying, sitting or standing. Enough, however, has been said already in the chapter on the use of apparatus (see Chapter IX (The Use Of Apparatus For Exercise)) to indicate the main points. Detail must be worked out for each individual patient.

There are, however, two points which call for special emphasis. The first is that the one essential function of the quadriceps is to maintain the stability of the knee-joint in full extension. Lack of appreciation of this point may be a source of complete failure in the attempt to restore the use of the limb. The importance of restoring power to the lower and inner fibres of the vastus internus has already been indicated (see p. 182). What part is played by each individual member of the quadriceps group at each phase of movement from full flexion to full extension has, so far as I know, not been elucidated. If we watch the muscle action of a well-developed and uninjured limb, we cannot help noticing the wave-like contraction in co-ordinated sequence of the various muscle elements. It is not improbable that each element plays a predominant part only during certain definite set phases of the movement. This much at least is certain, that, if the power of full extension is incomplete, and if we ignore special training to rectify the incapacity, recovery is often indefinitely postponed. It is for this reason that I always teach that the most important phases in the ordinary heels-raising, knees-bending exercises are the beginning and the end, namely the bracing backwards of the knees when first rising on tiptoe and again before finally sinking to the rest position. The one thing to aim at securing, therefore, is the power of full extension. When this is done, and not before, training may be undertaken through an ever-increasing range. The test as to whether it is safe to increase the range is simply this. It is unwise to set or allow any exercise which the patient fails to complete by securing full extension. Increase in the range of flexion of a knee is useless unless full extension can be secured with ease from each degree of flexion that is secured.1

The second important point when training a quadriceps is that, while using apparatus, it is possible to set the weakened muscle an invaluable exercise by attaching the sound limb to the weight and pulley. The patient is then compelled not only to stand on the weakened limb but also to balance his weight upon it, and this balance work depends on stability of the knee and on perfect control of the muscles that regulate its movements. When the sound limb is hitched on to the apparatus the balance work performed by its fellow is unconscious - often a great asset in treatment. This is one of the examples of what is referred to in the preface as gaining our end "by stealth."

1 The study of a recent case has tended to confirm the opinion that each element in the quadriceps mass has a preponderating function at different stages of movement. In this instance the rectus femoris seemed to play its most prominent part in extending the knee-joint from full flexion to about 45° (or rather less) short of full extension.