SACRO-ILIAC JOINT. 



335 



(c) Those by which the sacrum articulates with the last lumbar vertebra 



(Lumbo-sacral joints) ; 



(d) Those by which the hip bones are attached to the vertebral column 



(Sacro-iliac joints) ; 



(e) That by which the hip bones are attached to each other (Symphysis 



pubis). 



ARTICULATIONES SACROLUMBALES. 



Lumbo-sacral Joints. The articulation of the sacrum with the fifth lumbar 

 vertebra is constructed precisely on the principle ^of the articulations between two. 

 typical vertebrse, and the usual ligaments associated with such joints are repeated. 

 There is, however, an additional accessory ligament, termed the lateral lumbo-sacral 

 ligament. This extends from the anterior aspect of the inferior border of the 

 transverse process of the last lumbar vertebra, downwards and slightly laterally, 

 to the front of the lateral aspect of the ala of the sacrum, close to the sacro- 

 iliac joint. Further, a variable membranous band extends between the lateral 

 aspect of the inferior part of the body of the last lumbar vertebra and the front of 

 the ala of the sacrum. This band lies in front of the anterior ramus of the fifth 

 lumbar nerve. 



ARTICULATIO SACROILIACA. 



Each hip bone articulates with the sacral section of the vertebral column on 

 each side through the intervention of a diarthrosis, termed the sacro-iliac joint. 



Ilium 



Sacrum 



Greater sciatic 

 foramen 



Posterior sacro-iliac 

 ligament 



Sacro-iliac joint 



Sacro-tuberous 

 ligament 



Sacro-spinous 

 ligament 



Lesser sciatic foramen 



Acetabulum 



Sacro-tuberous 

 ligament 



Interpubic fibro-cartilage 



FIG. 313. FRONTAL SECTION OF PELVIS. 



This joint is formed between the contiguous auricular surfaces of the sacrum 

 and ilium. Each of these surfaces is more or less completely clothed with hyaline 

 articular cartilage. The joint cavity, which is little more than a capillary interval, 

 may be crossed by fibrous bands. 



