THE HIP-JOINT. 



339 



The various ligaments passing between the last lumbar vertebra and the sacrum and ilium 

 retain the weight of the trunk in. position upon the anterior end of the sacrum, and resist its 

 tendency to slip forwards and downwards towards the pelvic cavity. The entire weight of the 

 trunk and pelvis is transmitted to the heads of the thigh bones in the most advantageous 

 position, both for effectiveness and the strengthening of the inverted back of the hip bones, for it 

 will be evident that the heads of the femora thrust inwards upon the convex side of the arch, 

 very much at the place where the arches are weakest, viz., at the springing of the arch from its 

 piers. The forces which tend to cause movement of the pelvic bones during parturition act from 

 within the pelvis, and have for their object the increase of the various pelvic diameters, in 

 order that the foetal head may more readily be transmitted. For this purpose the wedge-like 

 dorsal surface of the sacrum is driven backwards, and a certain amount of extra space may there- 

 by be obtained. An important factor, however, in the increase of the pelvic capacity at this 

 period is found in the relaxation of its various ligaments. 



, 



ARTICULATIONES EXTKEMITATIS INFERIORS. 



ARTICULATIO 



Ischial spine 



'he Hip- Joint. The human body provides no more perfect example of an 

 enarthrodial diarthrosis than the hip-joint. Combined with all that variety of 

 movement which characterises a multi-axial joint, it nevertheless presents great 

 stability, which has been obtained by simple arrangements, for restricting the range 

 pf its natural movements. This stability is of paramount importance for the 

 ; maintenance of the erect attitude, and the mechanical adaptations whereby this 

 result is obtained are such that the erect attitude may be preserved without any 

 ^reat degree qf sustained muscular effort. 



Articular Surfaces. The head of the femur is globular in shape, and consider- 

 ably exceeds a hemisphere. 

 It is clothed with hyaline 

 articular cartilage on those 

 parts which come into direct 

 contact with the acetabulum. 

 There is frequently more or 

 less of extension of the 

 particular cartilage from the 

 [head to the adjoining anterior 

 I part of the neck, an extension 

 b which is accounted for by the 

 Islose and constant apposition 

 jf )f this portion of the neck 

 Itfith the posterior aspect of 



:he ilio - femoral ligament. 

 Irhe limit of the articular 

 partilage covering the head 

 f:.s indicated by a sinuous 

 l)order. Further, there is an 

 ftjibsence of articular cartilage 

 iii'rom the fovea or pit on 



he head of the femur. 



The acetabulum is a deep 

 i up-shaped cavity which pre- 

 ^ents a notch on its antero- 



nferior margin. The interior 

 I'f the cup is lined with a 

 i.ibbon-like band of articular 

 i iartilage which extends to 

 rhe brim of the cavity, but 



oes not cover its floor. This articular ribbon-shaped band is widest on its supero- 

 ^lOsterior aspect, and narrowest at the anterior margin of the acetabular notch. 

 Lig. Transversum Acetabuli. The transverse ligament (Fig. 315) bridges the 



cetabular notch, and consists of strong transverse fibres which are attached to 



Transverse acetabular ligament 



Retinacula 



FIG. 315. DISSECTION OF THE HIP- JOINT. 



Bottom of the acetabulum removed, and capsule of the joint thrown 

 laterally towards the trochanters. 



