THE KNEE-JOIXT 



253 



The ilio-fenioral band also i)revents the tendency of the trunk to roll l)ackwarils 

 on the thigh bones in the erect posture, and so does away with the necessity 

 for muscular power for this purpose; it is put on stretch in the stand-at-ease 

 position. 



The ligamentuni teres is of little use in resisting violence or in imparting strength 

 to the joint. It assists in checking rotation outAvards, and adduction during flexion. 

 A ligament can only be of use when it is tight, and it was found by trephining the 



Fig. 244.— LiGAMEXTrM Teres, brawx tight ix Flexion combixed with Rotation 



OUTWARDS AXD ADDUCTION. 



bottom of the acetabulum, removing the fat, and threading a piece of whipcord 

 round the ligament, that the ligament was slack in simple flexion, and very 

 loose in complete extension, but that its most slack condition was in al)duction. 

 It is tightest in flexion combined Avith adduction and rotation outwards, and 

 almost as tight in flexion with outward rotation alone, and in flexion with 

 adduction alone (figs. 242 to 244 J. 



2. THE KXEE-JOIXT 



Class . — Diarth rosis. 



Subdivision. — Giaglymus. 



The knee is the largest joint in the body. It is rightly described as a gingly- 

 moid joint, but there is also an arthrodial element; for, in addition to flexion and 

 extension, there is a sliding backwards and forwards of the tibia upon the femoral 

 condyles, as well as slight rotation round a vertical axis. It is one of the most 

 superficial, and, as far as adaptation of the bony surfaces goes, one of the weakest 

 joints, for in no position are the bones in more than partial contact. Its strength 

 lies in the number, size, and arrangement of the ligaments, and the powerful 

 muscles and fascial expansions which pass over the articulation and enal:)le it to 

 withstand the leverage of the two longest bones in the body. It may be said to 

 consist of two articulations Avith a common synovial membrane — the patello- 

 femoral and the tibio-femoral, the latter being double. It is comi)Osed of the 

 condyles and trochlear surface of the femur, the tuberosities of the tibia, and tlie 

 patella, united by the following ligaments, which may be divided into an external 

 and internal set: — 



