PELVIS 617 



ment). The sacro-tuberous ligament has a wide attachment 

 to the posterior superior and posterior inferior iliac spines and 

 to the side of the sacrum and coccyx. Narrowing consider- 

 ably as it proceeds downwards and forwards, it again expands, 

 and is inserted into the medial border of the tuberosity of the 

 ischium. From this it sends upwards a sharp falciform edge, 

 which extends forwards for a short distance upon the inferior 

 ramus of the ischium, and gives attachment to the parietal 

 pelvic fascia. It should be noticed that at its ischial attach- 

 ment some of the fibres of the ligament pass continuously 

 into the tendon of the biceps femoris muscle. 



Ligamentum Sacrospinosum (O.T. Small Sacro-sciatic Liga- 

 ment}. The sacro-spinous ligament is triangular in form. By 

 its base it is fixed to the side of the sacrum and coccyx in 

 front of the sacro-tuberous ligament, the fibres of both 

 mingling together ; by its apex it is attached to the spine 

 of the ischium. The pelvic surface of this ligament presents 

 an extremely intimate connection with the coccygeus muscle ; 

 indeed, it is generally believed that the ligament is derived 

 from the posterior part of the muscle by the fibrous degenera- 

 tion of its fasciculi. 



The sacro-tuberous and the sacro-spinous ligaments 

 convert the sciatic notches of the hip bone into foramina. 

 Through the great sciatic foramen pass the superior glutaeal 

 vessels and nerve, the piriformis muscle, the pudendal and 

 inferior gluteal vessels and nerve, the nerve to the obturator 

 internus, and the nerve to the quadratus femoris. 



The small sciatic foramen transmits the tendon of the 

 obturator internus muscle, the pudendal vessels and nerve, 

 and the nerve to the obturator internus muscle. 



The sacro-iliac joint is a diarthrodial joint. The ligaments 

 of the joint should now be divided, and the two bones forcibly 

 wrenched asunder. It will then be seen that each articular 

 surface is covered with a plate of cartilage, and that a small 

 synovial space intervenes between and partially separates 

 the two plates. 



The sacro-iliac joint is not immovable, as is sometimes 

 stated. A slight amount of movement can take place the 

 sacrum rotating round an imaginary line drawn transversely 

 through its second piece from one side to the other. In 

 the erect posture the promontory of the sacrum is withdrawn 

 to the full extent from the symphysis ; when the body is bent 



