328 



THE ARTICULATIONS, OR JOINTS 



muscle; between the lesser trochanter and the Quadratus femoris muscle; and there are burste 

 beneath the Biceps femoris muscle. 



Movements. The movements of the hip are very extensive, and consist of flexion, exten- 

 sion, adduction, abduction, circumduction, and rotation. 



The hip-joint presents a very striking contrast to the shoulder-joint in the much more com- 

 plete mechanical arrangements for its security and for the limitation of its movements. In the 

 shoulder, as we have seen, the head of the humerus is not adapted at all in size to the glenoid 

 cavity, and is hardly restrained in any of its ordinary movements by the capsular ligament. In 

 the hip-joint, on the contrary, the head of the femur is closely fitted to the acetabulum for a 

 distance extending over nearly half a sphere, and at the margin of the bony cup it is still more 

 closely embraced by the cotyloid ligament, so that the head of the femur is held in its place by 

 that ligament even when the fibres of the capsule have been quite divided (Humphry). The 

 anterior portion of the capsule, described as the iliofemoral ligament, is the strongest of all 

 the ligaments in the body, and is put on the stretch by any attempt to extend the femur 

 beyond a straight line with the trunk. That is to say, this ligament is the chief agent in main- 

 taining the erect position without muscular fatigue; for a vertical line passing through the 



FIG. 264. Relation of muscles to the capsule of the hip-joint. (From a drawing by Mr. F. A. Barton.) 



centre of gravity of the trunk falls behind the centres of rotation in the hip-joint, and therefore 

 the pelvis tends to fall backward, but is prevented by the tension of the iliofemoral and capsular 

 ligaments. The security of the joint may be also provided for by the two bones being directly 

 united through the ligamentum teres; but it is doubtful whether this so-called ligament can have 

 much influence upon the mechanism of the joint. Flexion of the hip-joint is arrested by the 

 soft parts of the thigh and abdomen being brought into contact when the leg is flexed on the 

 thigh; and by the action of the Hamstring muscles when the leg is extended. 1 Extension is 

 arrested by the tension of the iliofemoral ligament and the front of the capsule; adduction, 

 by the thighs coming into contact; adduction with flexion, by the outer band of the iliofemoral 

 ligament, and the outer part of the capsular ligament; abduction, by the inner band of the ilio- 

 femoral ligament and the p'ubofemoral band; rotation outward, by the outer band of the iliofemoral 

 ligament; and rotation inward, by the ischiocapsular ligament and the hinder part of the cap- 

 sule. The muscles which flex the femur on the pelvis are the Psoas, Iliacus, Rectus femoris, 

 Sartorius, Pectineus, Adductor longus and brevis, and the anterior fibres of the Gluteus medius 



1 The hip-joint cannot be completely flexed, in most persons, without at the same time flexing the knee, on 

 count of the shortness of the Hamstring muscles. Cleland, Jour, of Anat. and Physiol., No. 1, Old Series, p. 87. 



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