THE HIP-JOINT. 



269 



resistance is required, than below and internally, where it is thin, loose, and 

 longer than in any other part. It consists of two sets of fibres, circular and 

 longitudinal. The circular fibres (zona orbicularis} are most abundant at the lower 

 and back part of the capsule, and form a sling or collar around the neck of the 

 femur. Anteriorly they blend with the deep surface of the ilio-femoral ligament, 

 and through its medium reach the anterior inferior spine of the ilium. The 

 longitudinal fibres are greatest in amount at the upper and front part of the cap- 



FIG. 179. Left hip-joint laid open. 



sule. where they form distinct bands or accessory ligaments, of which the most 

 important is the ilio-femoral. The other accessory bands are known as the pubo- 

 femoral, passing from the ilio-pectineal eminence to the front of the capsule ; and 

 ischio-capsular, passing from the ischium, just below the acetabulum, to blend 

 with the circular fibres at the lower part of the joint. The external surface 

 (Fig. 164, page 241) is rough, covered by numerous muscles, and separated in 

 front from the Psoas and Iliacus by a synovial bursa, which not infrequently 

 communicates, by a circular aperture, with the cavity of the joint. It differs from 

 the capsular ligament of the shoulder in being much less loose and lax, and in not 

 being perforated for the passage of a tendon. 



The Ilio-femoral Ligament (Figs. 164 and 180) is an accessory band of fibres 

 extending obliquely across the front of the joint ; it is intimately connected with 

 the capsular ligament, and serves to strengthen it in this situation. It is attached, 

 above, to the lower part of the anterior inferior spine of the ilium; and, diverging 

 below, forms two bands, of which one passes downward to be inserted into the 

 lower part of the anterior intertrochanteric line; the other passes downward and 

 outward to be inserted into the upper part of the same line and adjacent part of the 

 neck of the femur. Between the two bands is a thinner part of the capsule. 

 Sometimes there is no division, but the ligament spreads out into a flat, triangular 

 band, which is attached below into the whole length of the anterior intertrochan- 

 teric line. This ligament is frequently called the Y-shaped ligament of Bigelow; 



