188 



THE ARTICULATIONS OF THE LOWER LIMB. 



RESSION OF 

 INT. FIBRO-CART. 



IMPRESSION OF 

 EXT 



Movements, &c. In order to explain the nature of the movements, it is necessary to 

 state some considerations with regard to the relations of the several parts of the knee-joint 

 to each other. The knee-joint may be regarded as consisting of three articulations conjoined, 

 viz., that between the patella and femur, and two others, one between each condyle of the 

 femur and the tibia. In many mammals the synovial membranes of these three joints are 

 either completely distinct or communicate with each other by only small openings. In the 

 human subject the mucous ligament is an indication of this separation of the synovial 

 cavities of the inner and outer joints, and the crucial ligaments may be looked upon as the 

 external and internal lateral ligaments of those two joints respectively. On the cartilage- 

 covered articular surface of the femur also a corresponding subdivision into three parts is to 



be recognised, the trochlear sur- 

 face for the patella being sepa- 

 rated from the convex tibial 

 surfaces by two shallow trans- 

 verse grooves which receive the 

 fibre-cartilages in the extended 

 position of the joint ; but along 

 the inner margin of the intercon- 

 dylar fossa there is marked off 

 from the rest of the internal 

 condyle a narrow semilunar facet 

 which is in contact with the in- 

 nermost facet of the patella in 

 extreme flexion. 



The movement of the patella 

 on the femur is one partly of 

 gliding, partly of coaptation. This 



Fig. 214. -LOWER EXTREMITY OF THE RIGHT FEMUR, FROM is ^A by a careful exami- 

 BELPW. (Drawn by T. W. P. Lawrence.) \ natlon of the M**lar surface of 



the patella, which is not uniformly 

 curved from above downwards, as 



it would be, were the movement one of gliding only, but exhibits on each side of the 

 vertical ridge three very slightly depressed surfaces, separated by two slight transverse 

 elevations, and along the inner margin a seventh area, upon which the transverse lines do not 

 encroach. "When the knee is extended, and the patella . drawn upwards by the extensor 

 muscles, the two inferior facets of the patella are in contact with the upper margin of the 



INTERCONDYLAR FOSSA 

 POST. CR.UC. LIOT. 



Fig. 215. RIGHT PATELLA, FROM BEHIND. (Drawn by 

 T. W. P. Lawrence.) \ 



The articular surface is 'seen, divided by a ridge into a smaller 

 internal and a larger external part. On each of these three facets 

 may be recognized, of which the middle is the largest and the lower 

 the smallest, while along the inner margin there is a narrow seventh 

 facet. 



trochlear surface ; in semiflexion the middle facets only are in 

 contact with the femur ; in greater flexion, the superior parts 

 of the patella are in contact with the lower parts of the troch- 

 lear surface ; and in extreme flexion the patella, which has been gradually turned outwards 

 by the increasing prominence of the inner condyle. rests by its innermost facet against the 

 semilunar surface on the outer margin of the internal condyle, and by its upper and outer 

 facet on the fore part of the external condyle. 



The articulation between each condyle and the opposed almost flat surface of the tibia, 

 while resembling, is not exactly a hinge- joint, and extension and flexion, the movements of 

 which it is capable, are produced by a combination of gliding, rolling, and rotation. If the 

 condyles of the femur be examined as they rest upon the tibia in the flexed position of the 

 joint, it will be seen that the inner condyle is longer than the outer, and that its anterior 

 portion inclines obliquely outwards to reach the patellar surface. In the movement of 

 extension the condyles move parallel to one another, both gliding and rolling until extension 

 is nearly completed, and then, the anterior part of the rolling surface of the external condyle 

 having already come into full contact with the tibia, the inner condyle continues to glide 

 backwards, bringing its oblique anterior part into contact with the tibia, so that the femur is 

 rotated inwards on the tibia. Similarly, the beginning of flexion is accompanied by a 

 rotation outwards of the femur, or inwards of the tibia. In complete extension the lateral 

 ligaments, the posterior ligament, and the anterior crucial ligament are tight, while the 



