Applied anatomy and kinesiology, the mechanism of muscular movement . 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 th
Applied anatomy and kinesiology, the mechanism of muscular movement . 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 inner and outer hamstrings when the foot. Fig. 104.—The so-called tendinous action of the two-joint muscles of the thigh:R, rectus femoris; P, psoas; Gl, gluteus maximus; If, hamstring; T, anterior tibial;O, gastrocnemius. (Lombard.) rests on the floor in normal position, but as soon as the tibia isrotated in either direction the opposing tendon loses tension, inspite of the fact that the rotation of the tibia would increase itstension if the tone of the muscle were not diminished by nervousinfluence. We have noticed that the rectus femoris and the hamstringmuscles reach past two joints—the hip and knee; this fact has led VASTUS INTERMEDWS 183 to their being called two-joint muscles to distinguish them fromthe one-joint muscles, which cross but one joint. Besides theactions we have studied thus far, and which may be called theindividual actions of these muscles, the two-joint muscles of thethigh have a combined action due to their passing across the oppo-site sides of the two joint
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