420 THE INFERIOR EXTREMITY 



the formation of the acetabulum, and at birth they are separated 

 from one another by a triradiate bar of cartilage. Secondary 

 centres of ossification appear in this cartilage about the twelfth 

 year, and the acetabulum is completely ossified by the sixteenth 

 or seventeenth year (Fig. 126). 



The articular cartilage forms a broad strip round the 

 acetabulum near its circumference, but the floor of the cavity 

 and the acetabular (cotyloid) notch are non-articular. 



At birth the proximal end of the femur is entirely cartil- 

 aginous. The neck of the femur is ossified by a proximal 

 extension from the diaphysis, and, as it forms, it divides the 

 cartilaginous extremity into two parts, which it separates from 

 one another. The more proximal of these forms the head. A 

 centre of ossification appears in it during the first year, and it 

 unites with the neck during the twentieth year. The more 

 distal forms the greater trochanter, which begins to ossify in 

 the second year and joins the shaft at 19. The secondary 

 centre for the lesser trochanter, which unites with the shaft 

 at 1 8, does not appear till the eighth to the twelfth year. 



The articular head of the femur forms rather more than 

 half a sphere. A little below and behind its centre there is a 

 non-articular depression for the attachment of the ligamentum 

 teres. 



The Labrum Glenoidale (cotyloid ligament) is a strong 

 fibre-cartilaginous ring attached to the circumference of the 

 acetabulum, and serving both to deepen its cavity and to reduce 

 the diameter of its inlet. It is accurately fitted round the head 

 of the femur, and even after the joint has been opened it is 

 not easy to pull the head of the femur out of the acetabulum. 



The Transverse Ligament bridges across the acetabular 

 notch, and completes the circumference of the acetabulum. 



The Capsule of the hip- joint is of great strength. Proximally, 

 it is attached to the bony circumference of the acetabulum, 

 the labrum glenoidale, and the transverse ligament (Fig. 125). 

 Distally, it is attached to the neck of the femur ; anteriorly, 

 this attachment is along the intertrochanteric line; but pos- 

 teriorly, it crosses the middle of the femoral neck i.e. the whole 

 of the anterior surface and the medial half of the posterior 

 surface of the femoral neck lie within the capsule. 



The capsule is strengthened by certain accessory ligaments. 



i. The Ilio-Femoral Ligament is a well-marked thickening 

 of the anterior aspect of the capsule. It is attached proximally 



