MOVEMENTS OF HIP JOINT. 



603 



In the head of the femur is a pit into which the round ligament is in- 

 serted. 



The acetabulum is coated with cartilage at its circumference, except 

 opposite the notch, and touches the head of the femur by this part : the 

 articular surface is deep above, but gradually decreases towards the notch. 



Within the cartilage and close to the notch, is a mass of fat (fig. 191, 

 f) covering about one third of the area of the cotyloid cavity, which 

 constitutes the gland of Havers : 

 it communicates with the fat of 

 the thigh beneath the transverse 

 ligament. 



Movement. In this ball and 

 socket joint there are the same 

 kinds of movement as in the 

 shoulder, viz., flexion and exten- 

 sion, abduction and adduction, 

 circu induction, and rotation. 



Flexion and extension. In the 

 swinging movement flexion is 

 freer than extension, the thigh 

 being capable of such elevation 

 as to touch the belly. 



During swinging the head of 

 the femur revolves in the bottom 

 of the acetabulum, rotating around 

 a line corresponding with the axis 

 of the head and neck ; and the 

 rapidity and extent of the move- 

 ments do not endanger the secu- 

 rity of the joint, the head of the 

 bone not having any tendency to 

 escape. 



In flexion, the back of the 

 capsule and the ilio-trochanteric 

 band are put on the stretch ; and 

 in extension, the strong ilio and 

 pubio-femoral bands are tightened. 



In abduction and adduction the femur is removed from, or brought 

 towards the middle line of the body. Of the two, abduction is the most 

 extensive, because the limb may soon meet its fellow when it is moved 

 inwards, though, if it is carried in front of the other, adduction is con- 

 siderable. 



In both states the head moves in the opposite direction to the shaft. 

 Thus, as the femur is abducted, the head descends, and the greater part 

 of the articular surface projects below the acetabulum; and when the 

 limb is raised to its utmost the great trochanter comes to rest on the 

 margin of the acetabulum, so as to limit farther motion. As the limb 

 descends and approaches the other, the head rises into the socket of the 

 joint, and is securely lodged, finally, in the deepest part of the cavity. 



In abduction, the inner band of the capsule is tightened over the pro- 

 jecting head of the femur, the upper part being relaxed. And in adduc- 

 tion, the outer band of the capsule is rendered tense enough to arrest the 

 movement. 



HIP JOINT OPENED, to show the interarticular or 

 round ligament. 



a. Part of the capsule. 



J. Ligamentum teres: c, its pubi, and, d, Us 

 ischial attachment. 



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