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Henry Gray (1825–1861).  Anatomy of the Human Body.  1918.
 
  The hip-joint presents a very striking contrast to the shoulder-joint in the much more complete mechanical arrangements for its security and for the limitation of its movements. In the shoulder, as has been seen, the head of the humerus is not adapted at all in size to the glenoid cavity, and is hardly restrained in any of its ordinary movements by the capsule. In the hip-joint, on the contrary, the head of the femur is closely fitted to the acetabulum for an area extending over nearly half a sphere, and at the margin of the bony cup it is still more closely embraced by the glenoidal labrum, so that the head of the femur is held in its place by that ligament even when the fibers of the capsule have been quite divided. The iliofemoral ligament is the strongest of all the ligaments in the body, and is put on the stretch by any attempt to extend the femur beyond a straight line with the trunk. That is to say, this ligament is the chief agent in maintaining the erect position without muscular fatigue; for a vertical line passing through the center of gravity of the trunk falls behind the centers of rotation in the hip-joints, and therefore the pelvis tends to fall backward, but is prevented by the tension of the iliofemoral ligaments. The security of the joint may be provided for also by the two bones being directly united through the ligamentum teres; but it is doubtful whether this ligament has much influence upon the mechanism of the joint. When the knee is flexed, flexion of the hip-joint is arrested by the soft parts of the thigh and abdomen being brought into contact, and when the knee is extended, by the action of the hamstring muscles; extension is checked by the tension of the iliofemoral ligament; adduction by the thighs coming into contact; adduction with flexion by the lateral band of the iliofemoral ligament and the lateral part of the capsule; abduction by the medial band of the iliofemoral ligament and the pubocapsular ligament; rotation outward by the lateral band of the iliofemoral ligament; and rotation inward by the ischiocapsular ligament and the hinder part of the capsule. The muscles which flex the femur on the pelvis are the Psoas major, Iliacus, Rectus femoris, Sartorius, Pectineus, Adductores longus and brevis, and the anterior fibers of the Glutæi medius and minimus. Extension is mainly performed by the Glutæus maximus, assisted by the hamstring muscles and the ischial head of the Adductor magnus. The thigh is adducted by the Adductores magnus, longus, and brevis, the Pectineus, the Gracilis, and lower part of the Glutæus maximus, and abducted by the Glutæi medius and minimus, and the upper part of the Glutæus maximus. The muscles which rotate the thigh inward are the Glutæus minimus and the anterior fibers of the Glutæus medius, the Tensor fasciæ latæ and the Iliacus and Psoas major; while those which rotate it outward are the posterior fibers of the Glutæus medius, the Piriformis, Obturatores externus and internus, Gemelli superior and inferior, Quadratus femoris, Glutæus maximus, the Adductores longus, brevis, and magnus, the Pectineus, and the Sartorius.
 
7b. The Knee-joint
 
  
(Articulatio Genu)


The knee-joint was formerly described as a ginglymus or hinge-joint, but is really of a much more complicated character. It must be regarded as consisting of three articulations in one: two condyloid joints, one between each condyle of the femur and the corresponding meniscus and condyle of the tibia; and a third between the patella and the femur, partly arthrodial, but not completely so, since the articular surfaces are not mutually adapted to each other, so that the movement is not a simple gliding one. This view of the construction of the knee-joint receives confirmation from the study of the articulation in some of the lower mammals, where, corresponding to these three subdivisions, three synovial cavities are sometimes found, either entirely distinct or only connected together by small communications. This view is further rendered probable by the existence in the middle of the joint of the two cruciate ligaments, which must be regarded as the collateral ligaments of the medial and lateral joints. The existence of the patellar fold of synovial membrane would further indicate a tendency to separation of the synovial cavity into two minor sacs, one corresponding to the lateral and the other to the medial joint.
  The bones are connected together by the following ligaments:
The Articular Capsule.
The Anterior Cruciate.
The Ligamentum Patellæ.
The Posterior Cruciate.
The Oblique Popliteal.
The Medial and Lateral Menisci.
The Tibial Collateral.
The Transverse.
The Fibular Collateral.
The Coronary.

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