OF THE PELVIS. 



241 



of the last lumbar vertebra, passes obliquely outward, and is attached below to 



the lateral surface of the base of the sacrum, becoming blended with the anterior 



sacro-iliac ligament. This ligament is in relation, in front, with the Psoas muscle. 



The Ilio-lumbar Ligament (Fig. 164) passes horizontally outward from the 



Aperture of communication 



with. 

 Bitrsn of PSOAS and ILIAOUS. 



Femur. ' 



FIG. 164. Articulations of pelvis and hip. Anterior view. 



apex of the transverse process of the last lumbar vertebra to the crest of the ilium 

 immediately in front of the sacro-iliac articulation. It is of a triangular form, 

 thick and narrow internally, broad and thinner externally. It is in relation, in 

 front, Avith the Psoas muscle ; behind, with the muscles occupying the vertebral 

 groove ; above, with the Quadratus lumborum. 



X. Articulations of the Pelvis. 



The ligaments connecting the bones of the pelvis with each other may be 

 divided into four groups : 1. Those connecting the sacrum and ilium. 2. Those 

 passing between the sacrum and ischium. 3. Those connecting the sacrum and 

 coccyx. 4. Those between the two pubic bones. 



1. ARTICULATIONS OF THE SACRUM AND ILIUM. 



The sacro-iliac articulation is an amphiarthrodial joint, formed between the 

 lateral surfaces of the sacrum and ilium. The anterior or auricular portion of each 

 articular surface is covered with a thin plate of cartilage, thicker on the sacrum 

 than on the ilium. These are in close contact with each other, and to a certain 

 extent united together by irregular patches of softer fibro-cartilage, and at their 

 upper and posterior part by fine fibres of interosseous fibrous tissue. In a con- 

 siderable part of their extent, especially in advanced life, they are not connected 

 together, but are separated by a space containing a synovial-like fluid, and hence 

 the joint presents the characters of a diarthrosis. 



The ligaments connecting these surfaces are the anterior and posterior sacro-iliac. 



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