166 ARTICULATIOXS OF THE LOWER LIMB. 



ening bands from the tendons of neighbouring muscles, in front from 

 the ilio-psoas, above from the long head of the rectus femoris, behind 

 from the gluteus minimus, and below from the obturator externus. 



From the inside of the capsule the inner layers of fibres are reflected 

 up\Yards from their insertion upon the neck of the femur to the articular 

 cartilage, forming a surface partly level and partly raised into longi- 

 tudinal folds called retinacula (Henle). 



The synovial membrane of the joint is reflected fi'om the neck of 

 the femur to the inner surface of the capsule, thence to the inner surface 

 of the cotyloid ligament and to the pad of fat in the bottom of the ace- 

 tabulum, from which it is further prolonged as a tubular investment 

 upon the round ligament. It frequently communicates through an 

 opening in the anterior wall of the capsule, with a synovial bursa placed 

 beneath the tendon of the ilio-psoas muscle. 



Movements. — The movements allowed at the liip-joint are extension, flexion, 

 abduction, adduction, circunaduction, and rotation. Extension is limited by the 

 anterior fibres of the capsular ligament, and the ilio-femoral band : flexion is 

 limited only by the contact of the neck of the femui- with the acetabulum. 

 Abduction is controlled by the pubo-femoral bands, and by the lower part of the 

 capsule ; adduction by the ilio -trochanteric band and by the upper part of the 

 capsule. The roimd ligament is put upon the stretch when the thigh is partially 

 flexed and adducted ; it therefore resists dislocation upwards and backwards on 

 the dorsum ilii, which is, notwithstanding its presence, the most frequent kind 

 of displacement. The round ligament is also put iipon the stretch in the position 

 of flexion and external rotation. The swinging antero-posterior movement of 

 the femm-, as in walking or running, is eft'ected by rotation of the head of the 

 bone in the hip-joint. In the erect attitude, as a vertical line passing through the 

 centre of gravity of the trunk falls behind the centres of rotation in the hip- 

 joints, the pelvis tends to fall backwards by over extension of the hip-joints, l:>ut 

 as this is prevented by the tightening of the capsule in front, the maintenance 

 of the erect attitude, without n^uscular effort, is partly due to this mechanism 

 of the hip-joint. 



THE KNEE-JOINT. 



The articular surfaces of this complicated joint are the condyles of 

 the femur and tibia, with fibro-cartilages interposed, the articulating 

 surface of the patella, and the patellar surface of the femur. The action 

 is mainly that of a hinge-joint. The joint is strengthened superficially 

 by fibrous coverings derived from the muscular tendons and apo- 

 ncnroscs. The ligaments which have received special names are the 

 following. 



The internal lateral ligament, long and flat, connects the internal 

 tuberosity of the femur with the inner tuberosity and the hinder l)order 

 of the tibia, on the shaft of which it descends for some distance. Supe- 

 riorly its deep surface rests on the articular synovial membrane; in the 

 middle it is attached to the internal semilunar cartilage ; and below the 

 head of the tibia the anterior slip of insertion of tlic semimembranosus 

 muscle passes between the ligament and the l)one. 



The external lateral ligament is a rounded cord, Avhich extends 

 from the external tuberosity of the femur to the head of the fibula. Its 

 internal surface corresponds with the tendon of the ]iopliteus muscle 

 and the inferior external articular vessels. The tendon of the liiceps 

 flexor cruris muscle is frequently divided into two by this ligament, and 

 between the ligament and the tendon there is a synovial bursa. Further 



