192 



THE ARTICULATIONS OF THE HORSE 



THE HIP JOINT 



This joint (Articulatio coxae) is an enarthrosis formed by the proximal end 

 of the femur and the acetabulum. 



Articular Surfaces. — The head of the femur presents an almost hemispherical 

 articular surface, which is continued a short distance on the upper surface of the 

 neck. It is more extensive than the socket which receives it. Internally it is 

 cut into by a deep notch for the attachment of the round and pubo-femoral liga- 

 ments. The acetabulum is a typical cotyloid cavity. Its articular surface is 

 somewhat crescentic, being deeply cut into internally by the acetabular notch and 



Fir.. 154. — Pelvic Ligaments and Hip Joint. 

 1, Dorsal sacro-iliac ligament; 2, lateral sacro-iliac ligament; S, sacro-.sciatic ligament; 4, greater sciatic 

 foramen; 6, lesser sciatic foramen; 6, line of attachment of intermuscular .septum between biceps femoris and semi- 

 tendinosus; 7, capsule of hip joint; S, rectus parvus or capsularis muscle; 9, outer tendon of origin of biceps 

 femoris; 10, internal, 11, external, angle of ilium; 12, shaft of ilium; IS, superior ischiatic spine; 14, pubis; i. 5, 

 tuber ischii; /(?, trochanter major; /7, semimembranosus; /S, fifth lumbar spine; /9, ;20, first and second coccygeal 

 vertebrse. 



fossa. It is increased and deepened by a ring of fibro-cartilage, the cotyloid 

 ligament (Labrum glenoidale), which is attached to the bony margin; that part of 

 the ligament which crosses the notch is called the transverse ligament (Fig. 456). 

 The joint capsule is roomy. It is attached around the margin of the acetab- 

 ulum and the neck of the femur. It is thickest externally. 



The attachment on the femur is about 1 cm. from the marsin of the articuhxr surface, except 

 above, where 2 to 3 cm. of the neck is intracapsular. A thin oblique bantl corresponding in direc- 

 tion with the rectus parvus muscle reinforces the antero-external part of the capsule; this appears 

 to be the feeble homologue of the very strong ilio-femoral ligament of man. The capsule is very 

 thin under the ilio-psoas, and is adherent to the muscle. Internally, its fibrous part is perforated 

 by the pubo-femoral and round ligaments and the articular vessels. 



