THE HIP-JOINT 



329 



and minimus. Extension is mainly performed by the Gluteus maximus, assisted by the Ham- 

 string muscles. The thigh is adducted by the Adductores magnus, longus, and brevis, the 

 Pectineus, the Gracilis, and the lower part of the Gluteus maximus, and abducted by the Gluteus 

 medius and minimus and the upper part of the Cluteus maximus. The muscles which rotate 

 the thigh inward are the anterior fibres of the Gluteus medius, the Gluteus minimus, and 

 the Tensor fasciae femoris; while those which rotate it outward are the posterior fibres of the 

 Gluteus medius, the Pyriformis, Obturator externus and internus, Gemellus superior and inferior, 

 Quadratus femoris, Iliacus, Gluteus maximus, the three Adductors, the Pectineus, and the 

 Sartorius. 



Surface Form. A line drawn from the anterior superior spinous process of the ilium to 

 the most prominent part of the tuberositv of the ischiunT( Xelaton'tt line) runs through il,,. 



~ 



.centre of the acetabulum. and would, therefore, indicate the level of the hip-joint: nr, in 

 words, the upper border of the great trochanter. which lies on Xelaton's line, is on a level with 

 the centre of the hip-joint. 



Applied Anatomy. Inflammation of burscE about the hip-joint gives rise to confusing 

 symptoms, and is not uncommonly mistaken for hip-joint disease. 



Great sacroscii 

 ligament. 



Small sacrosciatic 

 ligament. 



Great trochanter 

 of femur. 



Tuberosity of ischium 



FIG. 265. N^laton's line and Bryant's triangle. 



In dislocation of the hip " the head of the thigh bone may rest at any point around its socket" 

 (Bryant); but whatever position the head ultimately assumes, the primary displacement is 

 generally downward and inward, the capsule giving way at its weakest that is. its lower and 

 inner part. The situation that the head of the bone subsequently assumes is determined 

 by the degree of flexion or extension, and of outward o^ inward rotation of the thigh at the 

 moment of luxation, influenced, no doubt, by the iliofemoral ligament, which is not easily rup- 

 tured. When, for instance, the head is forced backward, this ligament forms a fixed axis, around 

 which the head of the bone rotates, and the head is thus driven on to the dorsum of the ilium. 

 The iliofemoral lig'ament also influences the position of the thigh in the various dislocations: 

 in the dislocations backward it is tense, and produces inversion of the limb; in the dislocation 

 on to the pubes it is relaxed, and therefore allows the External rotators to evert the thigh; while 

 in the thyroid dislocation it is tense and produces flexion. The muscles inserted into the upper 

 part of the femur, with the exception of the Obturator internus, have very little direct influence 

 in determining the position of the bone. Bigelow has endeavored to show that the Obturator 

 internus is the principal agent in determining whether in the backward dislocations the head 

 of the bone shall be ultimately lodged on the dorsum of the ilium or in or near the sciatic notch. 

 In both dislocations the head passes, in the first instance, in the same direction; but, as Bigelow 



