Applied anatomy and kinesiology, the mechanism of muscular movement . very short steps, which they lengthensomewhat without danger by swinging the hip forward as far aspossible at each step, giving them a waddling and stiff gait. Ifthey try to hurry or swing the foot too far forward they fall. Chil-dren with the extensors lost are apt to walk with the hands restingon the knees, so as to keep them from flexing by the use of thehands; this is laborious and leads to deformity of the trunk. Whatis still worse, after the extensors have been lost for some time theflexors shorten from lack of antagon
Applied anatomy and kinesiology, the mechanism of muscular movement . very short steps, which they lengthensomewhat without danger by swinging the hip forward as far aspossible at each step, giving them a waddling and stiff gait. Ifthey try to hurry or swing the foot too far forward they fall. Chil-dren with the extensors lost are apt to walk with the hands restingon the knees, so as to keep them from flexing by the use of thehands; this is laborious and leads to deformity of the trunk. Whatis still worse, after the extensors have been lost for some time theflexors shorten from lack of antagonism, keeping the knees flexedand making walking impossible. This makes it necessary to wear VASTUS INTERMEDIUS 181 an appliance that keeps the knee extended, and then the waddlingwalk described above can be executed. When the knee is flexed through 90 degrees or more it can berotated outward by contraction of the biceps and inward by thesemitendinosus, sartorius, and adductor gracilis, which attach tothe tibia together. This is easily observed by reference to ones. Fig. 103.—The extensors of the knee in action: Ii, rectus; E, vastus externus;7, vastus internus. own knee, while sitting with the feet on the floor and the kneesflexed to about 100 degrees. Place the hands on the sides of thethigh near the knee, the thumbs on top and the fingers beneath;notice the tendon of the biceps, plainly felt on the outer side, andthe tendons of the three muscles together on the inner side. Nowturn the toes forcibly outward and notice that the tendon of thebiceps springs into greater prominence and the inner group of 182 MOVEMENTS OF THE KNEE-JOINT tendons disappears under the finger-tips; reverse the rotation andnotice the reversal of the action of the muscles, as felt by thefinger-tips. This not only demonstrates the action of the musclesemployed in rotating the knee but also furnishes one of the bestillustrations of the inhibition of antagonists. It is easy to feel thetendons of both the
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