46 



NORMAL ANATOMY OF THE KNEE-JOINT. 



sixth of an inch, at the outer margin or thickest 

 part. They are both composed of concentric 

 fibres, the extremities of which are fixed to the 

 central parts of the head of the tibia, before and 

 behind the crucial ligaments, with whose fibres 

 they intermingle ; the anterior extremities are 

 usually joined together by a transverse liga- 

 ment, but this is sometimes wanting. 



The ligamentum patella, of vast importance 

 in the actions of the knee-joint, is yet the most 

 distant from its articular surfaces ; it extends, 

 broad and flat, from the lower somewhat point- 

 ed portion of the patella to the inferior part of 

 the tubercle of the tibia, being in the adult 

 about two inches in length. It forms a strong 

 inelastic but inflexible bond of union of the 

 patella with the tibia, and may with propriety 

 be looked upon as a continuation of the ex- 

 tensor tendons which are inserted into the 

 upper and lateral margins of the former bone; 

 some fibres indeed pass over its anterior sur- 

 face, but it is only through this bone and its 

 ligament that the extensor muscles can act 

 upon the leg. The patella is thus seen to be 

 placed in a situation analogous to that of the 

 sesamoid bones, in the tendons which play 

 over bony surfaces, in the hands and feet. The 

 ligament of the patella is covered anteriorly by 

 dense integument, and the fascia of the leg : 

 posteriorly a cushion of fat is interposed be- 

 tween it and the joint at the upper part, while 

 below it is separated from the bone by a bursa, 

 whose situation was pointed out in the descrip- 

 tion of the tibia. (Seefg. 1 1 1 , b, vol. i. p. 252.) 

 More closely applied to the joint are the lateral 

 ligaments, the posterior and the crucial liga- 

 ments; and portions of the synovial capsule which 

 are described by some anatomists as alar and 

 mucous ligaments. The lateral ligaments have 

 a vertical direction at each side of the knee, and 

 are placed nearer to the posterior than the ante- 

 rior boundary of the joint ; the upper attach- 

 ment is in fact to the tuberosity at the centre 

 of the smaller curve which the articular sur- 

 faces of the condyles form at their back part. 

 The internal lateral ligament descends from 

 the tuberosity of the internal condyle of the os 

 femoris to beneath the head of the tibia ; it is 

 nearly three inches in length, of a flattened 

 form, narrow at its commencement, but en- 

 larging considerably opposite the joint, to the 

 synovial membrane of which as well as to the 

 internal semilunar cartilage it adheres; infe- 

 riorly it again contracts in width. Its upper 

 attachment is covered by the fascia lata ; below, 

 it is inserted into the shaft of the tibia just 

 beneath the head of the bone, and anterior to 

 its inner angle ; and the tendons of the sarto- 

 rius, gracilis, and semitendinosus cross over it. 



The external lateral ligament (lig. luterale 

 externum) arises from the tuberosity on the 

 external condyle of the femur, and descends, 

 inclining backwards, partly covered by the 

 tendon of the biceps, to be inserted with it 

 into the head of the fibula ; the attachment of 

 its upper extremity is immediately above the 

 origin of the popliteus tendon, which it crosses 

 in its descent, so that this tendon enveloped by 

 its synovial sheath is situated between the liga- 



ment and the joint. The deviation of this 

 ligament from the perpendicular direction is 

 perceived most distinctly in the state of exten- 

 sion ; when the joint is flexed, the upper at- 

 tachment of the ligament is brought more into 

 the perpendicular over its fibular attachment, 

 the ligament is relaxed and assumes the per- 

 pendicular direction ; hence, in the flexed con- 

 dition of the joint, the external condyle of the 

 femur, or the tibia on it, admits of a more free 

 motion. This ligament is contrasted by its 

 less length and more rounded form with the 

 internal lateral, and is composed like it of 

 shining tendinous fibres ; a still shorter set of 

 fibres sometimes passes more posteriorly from 

 the condyle to the head of the fibula, or 

 from the sheath of the popliteus tendon, and 

 has been called the short external lateral liga- 

 ment. 



The posterior ligament (lig. posticum Win- 

 slowii) is a portion of the tendon of the semi- 

 membranosus muscle which is given off near 

 its insertion at the posterior and inner margin 

 of the head of the tibia ; the portion under con- 

 sideration forms a flat and dense fascia which 

 passes upwards and outwards to the external 

 condyle, where it becomes adherent to the sy- 

 novial capsule and mingling with the tendinous 

 origin of the outer head of the gastrocnemius : 

 posterior to it lie the popliteal vessels, and in 

 front of it there is a quantity of firm granulated 

 fat, into which some of its fibres penetrate. 



When the posterior ligament and the fat just 

 spoken of are removed, and the joint is ex- 

 tended, the two crucial ligaments (ligament a 

 cruciata* ) are brought into view ; they may be 

 seen on the anterior aspect by dissecting down 

 the patella from the fore part of the joint, and 

 putting it in a state of flexion ; in the former 

 view, the posterior crucial ligament is best 

 seen ; in the latter, the anterior : the upper 

 extremities of both are fixed in the fossa be- 

 tween the condyles of the os femoris; their 

 lower extremities are attached to the head of 

 the tibia between the two articular surfaces. 



The anterior crucial ligament passes from 

 the inner and back part of the outer condyle 

 downwards and forwards to the depression in 

 frontof the spine of the tibia, where some portion 

 becomes continuous with the anterior extre- 

 mity of the internal semilunar cartilage. The 

 posterior extends from the fore and outer part 

 of the internal condyle downwards and back- 

 wards to the notch at the posterior margin of 

 the head of the tibia, where it becomes like- 

 wise attached to the posterior extremity of the 

 external semilunar cartilage. The crucial liga- 

 ments thus derive their name from decussating 

 one another like the strokes of the letter X ; 

 the crossing is, however, considerably above 

 their centre : the anterior passes to the outer 

 side of the posterior. 



The synovial capsule^ entirely surrounds the 



* [It is useful to bear in mind that these ligaments 

 are called anterior and posterior with reference to 

 their insertions into the tibia, the one in front of, 

 the other behind, the spine of that bone. Ed.] 



t [Weber recommends as a good way of demon- 

 strating the full extent and connexions of the 



