336 



THE AKTICULATIONS OK JOINTS. 



The cavum articulare (joint cavity) is surrounded by ligaments of varying 

 thickness and strength, which constitute the fibrous stratum of its articular capsule. 

 Thus, its anterior part is thin, and consists of short but strong fibres which pass 

 between adjoining surfaces on the ala of the sacrum and .the iliac fossa of the 

 hip bone; they form the anterior sacro-iliac ligament. On the posterior aspect 

 there are three ligaments. The interosseous sacro-iliac ligament (Fig. 313) con- 

 sists of numerous strong fasciculi, which pass from the rough area on the medial 

 aspect of the ilium, above and behind its auricular surface, downwards and medially 

 to the tubercles of the transverse processes and the depressions behind the first and 

 second segments of the sacrum. This ligament is of great strength, and with its 



Ilio-lumbar ligament 



Short posterior saci 

 iliac ligament 



Long posterior 

 sacro-iliac ligament 



Reflected head of rectus femoris i 



Lesser sciatic 

 foramen 



Sacro-tuberous 

 ligament 



Obturator membrane 





FIG. 314. POSTERIOR VIEW OF THE PELVIC LIGAMENTS AND OF THE HIP-JOINT. 



fellow it is responsible for suspending the sacrum and the weight of the super- 

 imposed trunk from the hip bones. 



The long posterior sacro-iliac ligament (Fig. 314) is a superficial thickened portion 

 of the interosseous ligament. It consists of a definite band of fibres passing from 

 the posterior superior iliac spine to the tubercles of the transverse processes of the 

 third and fourth segments of the sacrum. 



The short posterior sacro-iliac ligament consists of superficial fibres of the 

 interosseous ligament passing from the posterior superior iliac spine to the tubercles 

 of the first and second transverse processes of the sacrum. 



The articular cavity of this joint is very imperfect and rudimentary. 



Several accessory ligaments are associated with the articulation of the hip bone 

 to the sacral section of the vertebral column. 



