340 THE AKTICULATIONS OE JOINTS. 



both of its margins, but more extensively to the postero-inferior. This ligament 

 does not entirely fill the notch, but leaves an open interval between its inferior 

 border and the bottom of the notch through which vessels and nerves enter the 

 cup. The acetabular aspect of this ligament constitutes an articular surface. 



The acetabulum is deepened by the labrum glenoidale (O.T. cotyloid ligament) 

 (Figs. 315 and 316), which consists of a strong ring of fibre-cartilaginous tissue 

 attached to the entire rim of the cup. The attached surface of the ring is broader 

 than its free edge, and, moreover, the latter is somewhat contracted, so that the 

 ligament grasps the head of the femur which it encircles. Its fibres are partly 

 oblique and partly circular in their direction. By the former it is firmly implanted 

 on the rim' of the acetabulum and the lig. transversum acetabuli; by the latter 

 the depth of the cup is increased through the elevation of its edge, and its 

 mouth slightly narrowed. By one surface this ligament is also articular. 



Capsula Articularis. An articular capsule (Figs. 315 and 316) completely 

 invests the joint cavity. Its fibrous stratum is of great strength, although it is not 

 of equal thickness throughout, being considerably thicker on the supero-anterior 

 aspect than at any other part. Unlike the corresponding structure of the shoulder- 

 joint, it does not permit of the withdrawal of the head of the femur from contact 

 with the acetabular articular surfaces, except to a very limited extent. Its fibres 

 are arranged both in the circular and in the longitudinal direction, the former, 

 known as the zona orbicularis, being best marked posteriorly, while the longitudinal 

 fibres stand out more distinctly in front, where they constitute special ligaments. 

 Looked at as a whole, the fibrous stratum of the capsule has the following 

 attachments : proximally it surrounds the acetabulum, on the superior-and posterior 

 aspects of which it is attached directly to the hip bone, while on the anterior and 

 inferior aspects it is attached to the non- articular surfaces of the labrum j 

 glenoidale and transverse ligaments of the acetabulum ; distally it encircles the neck j 

 of the femur, where it is attached in front to the intertrochanteric line ; above, to 

 the medial aspect of the root of the greater trochanter ; below, to the lower part 

 of the neck of the femur, in close proximity to the lesser trochanter; behind, to 

 the line of junction of the lateral and middle thirds of the neck of the femur. 

 It is a matter of some importance to note that only part of the posterior surface 

 of the neck of the femur is enclosed within the articular capsule. The femora] 

 attachments of the fibrous stratum of the capsule vary considerably in their 

 strength, being particularly firm above and in front, but much weaker below and 

 posteriorly, where the orbicular fibres are well seen. Many fibres of the fibrous 

 stratum, are reflected from its deep aspect proximally upon the neck of the femur, 

 where they form ridges, and to these the term retinacula (Fig. 315) is applied. 



The epiphyseal line of the head of the femur is intra-capsular ; the epiphyseal 

 lines of the two trochanters are extra-capsular. 



The longitudinal fibres of the fibrous stratum of the capsule are arranged so as tc 

 form certain definite bands, viz. : 



(1) Lig. Iliofemorale. The ilio- femoral ligament (Fig. 316) consists of 

 triangular set of fibres attached proximally, by their apex, to the inferior part 

 the anterior inferior iliac spine and the immediately adjoining part of the rim ol 

 the acetabulum, and distally, by their base, to the intertrochanteric line of the 

 femur. This ligament is the thickest part of the fibrous stratum, but its sides are 

 more pronounced than its centre, especially towards its base. Consequently the 

 ilio-femoral ligament presents some resemblance to an inverted Y (A), and therefore 

 was formerly named the Y-shaped ligament of Bigelow. 



The lateral or upper limb of the ilio-femoral ligament may be somewhat extended by th< 

 inclusion of additional longitudinal fibres, and described as the ilio-trochanteric ligament. Thi 

 band arises from the anterior part of the dorsum of the acetabulum, and extends to the femora 

 neck, close to the anterior end of the medial surface of the greater trochanter. 



(2) Lig. Pubocapsulare. The pubo-capsular ligament (Fig. 316) is composed o i 

 some bands of fibres of no great strength, which extend from the lateral end of th 

 superior ramus of the pubis, the ilio-pectineal eminence, the obturator crest and th< 

 obturator membrane, to lose themselves, for the most part, in the capsule, althougl 



