48 



ABNORMAL CONDITIONS OF THE KNEE-JOINT. 



bursa behind its ligament. It has been said 

 above that besides its ginglymoid motion, the 

 knee-joint has a slight arthrodial motion in the 

 bent position : this is strictly a rotation of the 

 tibia on its axis, and the effect is to point the 

 toes more or less to the outer side, rotation in- 

 wardly to any great extent being prevented by 

 the crucial ligaments. During this movement 

 of rotation, the inner articulating surface on 

 the head of the tibia advances forwards, while 

 at the same time the outer one recedes ; the 

 lateral ligaments allow of this motion, in con- 

 sequence of their inferior attachments being a 

 good deal below the margin of the joint ; and 

 the crucial ligaments permit the successive, 

 though not the simultaneous, advance or re- 

 cession of the cavities on the head of the tibia. 

 In all positions of the joint the arrangement is 

 such that the attempt to thrust forwards the 

 whole head of the tibia is resisted by the ante- 

 rior crucial ligament, whilst the posterior pre- 

 vents it from being driven backward.* The 



* [The following experiments, which may easily 

 be tried, illustrate the respective offices of the se- 

 veral ligaments. 



If the external fibrous investment of the joint 

 be completely removed, taking care that the lateral 

 and crucial ligaments shall be free from injury, 

 the motions of the joint will be in no degree af- 

 fected ; but if the opposite experiment be tried, 

 and the lateral and crucial ligaments be cut, leav- 

 ing the external fibrous investment uninjured, 

 excepting a small hole made for getting at the liga- 

 ments, it will be found that the integrity of the 

 joint is completely destroyed, the bones are but 

 loosely connected to each other, their apposition is 

 destroyed, and they move about indifferently in 

 every direction. 



Aa;ain, if after dissecting off the external fibrous 

 investment both crucial ligaments be cut, leaving 

 the lateral ligaments as the only bonds of con- 

 nection between the two bones, it is found that 

 during extension, the fixedness of the joint is un- 

 impaired, but if flexion be made gradually, the 

 bones becomes less in apposition and more move- 

 able, and in the completely bent state of the limb, 

 they become quite loosely connected and may rea- 

 dily be moved from side to side, and the only limit 

 to flexion is from the tibia coming against the 

 femur. 



If the lateral ligaments be cut, leaving the cru- 

 cial uninjured, the bones remain firmly connected 

 when the joint is in the state of complete flexion, 

 and the crucial ligaments still, as in the natural 

 state, oppose any further flexion. In the gradual 

 diminution of the flexion, the junction of the bones 

 becomes less complete, and when the extension 

 has been carried to its full extent, the bones may 

 be separated from each other, ami admit of lateral 

 motion ; and if the joint be held up so as to allow 

 the tibia to hang from it, the foot will become 

 everted by its own weight, and the two crucial liga- 

 ments, instead of their crossed and oblique position, 

 will assume a parallel and vertical direction. These 

 experiments are described by Weber, but there are 

 few anatomists in this country, for many years back, 

 who have not frequently tried them. 



The office of the semilunar cartilages is three- 

 fold : 1. filling up the empty space which the arti- 

 cular surfaces leave around their point of contact, 

 they distribute the pressure over a greater surface ; 

 2. they serve to distribute the tension of the liga- 

 ments in the movements of the joint more uni- 

 formly, and thereby to oppose any jarring of the 

 bones against each other; and, thirdly, they deaden 

 the vibrations which in the various movements of 



mucous ligament and fatty body of the joint 

 change their situation in some degree during 

 its motions and may serve to fill spaces which 

 which would otherwise be left vacant: the idea 

 that they are peculiarly concerned in secreting 

 the synovia has been satisfactorily refuted un- 

 der " ARTICULATION." 



The bursae in the neighbourhood of the knee- 

 joint are numerous and not unimportant, from 

 the circumstance that some of them often open 

 into the joint itself. In the layers of fascia 

 anterior to the patella, one or more exist, im- 

 perfectly formed and very liable to inflame and 

 suppurate. The situations in which the more 

 perfect specimens are found are as follow, viz. 

 behind the ligament of the patella; between 

 the cruralis and fore-part of the os femoris; 

 beneath the internal lateral ligament ; at the 

 insertion of the semitendinosus, gracilis, and 

 sartorius ; underneath each head of the gemel- 

 lus; and around the tendons of the semi-mem- 

 branosus and popliteus respectively ; the last- 

 named bursa is continued down some distance 

 between the popliteus and the tibia, and it 

 often communicates below with the superior 

 tibio-fibular articulation, as well as with the 

 knee-joint above. This joint is supplied with 

 blood from the popliteal artery by five different 

 branches, viz. two superior articular, which wind 

 round the lower part of the os femoris; one mid- 

 dle articular which passes through the posterior 

 ligament to the central parts of the joint; and 

 two inferior articular, which take their course 

 round the head of the tibia, and anastomose 

 freely with each other, and with the two upper; 

 the returning veins go to the popliteal. 



The comparative anatomy of the knee-joint 

 gives for the most part the same essential struc- 

 ture as we have described in man, though va- 

 riously modified. 



In most animals, when in a standing pos- 

 ture, the knee maintains habitually a state of 

 flexion, and this arrangement conduces much 

 to fleetness and agility of motion. In the ele- 

 phant, however, the bones of the hind leg form 

 an upright pillar of support, and the knee is ex- 

 tended as in the human subject. The elephant 

 also resembles man in the circumstance of the 

 knee being brought to the ground in kneeling ; 

 whereas, in most genera, the true knee is placed 

 much nearer to the body of the animal. 



(Alfred Higginson.) 



KNEE-JOINT, ABNORMAL CONDITIONS 



OF. The abnormal conditions of the knee- 

 joint may be arranged under those which result 

 from disease and accident. The deviations oc- 

 casionally met with as the consequence of con- 

 genital malformation are fortunately rare. 



DISEASE. The abnormal appearances in the 

 knee-joint resulting from disease are those which 

 spring from some specific irritation, such as 

 struma, gout, rheumatism, syphilis, or malig- 

 nant disease, or from direct violence. Most of 

 these irritations affect all the structures of the 



the limbs, especially in standing, walking, or run- 

 ning, are propagated along the bones. VideWeber, 

 Mechanik, &c. p. 193. Eu.J 



