The Lower Extremity and Pelvis 161 



on the back of each condyle, the segment of a larger circle becomes apparent below, and 

 a still larger one as the surface reaches the trochlear cartilage. 



The internal lateral ligament is a long and strong band from the inner condyle 

 (Fig. 122) to the tibia not very far above the level of the inner end of the oblique line 

 (Fig. 134). Its upper attachment is about the centre of one part of the curve in which 

 the tibia moves in flexion, as shown in Fig. 122, and over this portion the tibia is efficiently 

 held by ths ligament : behind this the tension of the posterior crucial ligament holds the 

 bones in apposition on the smaller curve. Observe that the internal lateral ligament 

 comes down far below the proper level of (coronary) capsular attachment (this is indi- 

 cated in Fig. 131) , and below this the ligament covers the insertion of Semimembranosus, 

 with a bursa over it, and is joined lower down by some fibres of the lower expansion 

 from this tendon. Here it also crosses the lower articular vessels. Where it lies on 

 the coronary fibres the ligament is attached to them, and through them has some 

 connection with the margin of the internal semilunar cartilage. 



FIG. 134. Right tibia, inner and posterior views. A, in the left-hand figure, is the subcutaneous inner 

 surface of the shaft, crossed by the long saphenous vein. This surface is thus smooth, and slightly 

 convex from side to side in conformity with the shape of the leg ; rather concave from above down in 

 its lower half, owing to the increasing prominence of the lower end. In its upper part, however, the 

 inner aspect of the bone shows secondary markings for Vastus internus, Gracilis (G), Sartorius (S), and 

 Semitendinosus (S-7~). These are all deep to the deep fascia, which must therefore be carried in by 

 them across the surface. Vastus internus is deep to the other three tendons, wherefore these, coming 

 from behind and above, are inserted below and in front of the Vastus ; see the middle figure, where 

 they are represented as a single insertion by a thick black line, and their situation over the Yastus and 

 internal ligament is shown by interrupted lines. Vastus internus has a strong band that makes a 

 definite rounded marking on the bone, the rest of its insertion being by more scattered fibres reaching 

 almost to the tubercle (see Fig. 131), among which the internal inferior artery turns upwards. Internal 

 lateral ligament is on the junction of inner and back surfaces, not very far above the inner end of the 

 oblique line. B, area covered by Popliteus but not affording insertion to it ; at the extreme inner end 

 of the triangular " popliteal surface " the bone is roughened by fibres, N, of Semimembranosus (expan- 

 sion) reaching the bone as far down as the ligament. Below the oblique line the Tibialis posticus and 

 Flexor longus digitorum mould the bone into surfaces in different planes, separated by the vertical 

 line ; both arise by muscle fibre and hence show no secondary markings in their areas as a rule, but 

 tendinous fibres in the upper part of Tib. post, may cause roughnesses near the upper part of the oblique 

 line (see Fig. 133 A). These deep flexors are covered in by the deep transverse fascia (fine green line). 

 Tibialis posticus is directed downwards and inwards from its origin, therefore is in relation with the 

 area C, while Flex. long, hallucis comes downwards and inwards from the fibula and lies on the area 

 D ; between these the main vessels and nerve and tendon of F. long. dig. come into relation with the 

 bone. 



When the tibia passes on to the large front curve, the internal ligament gets taut 

 at once, and so limits extension, like the anterior crucial ligament. 



The external lateral ligament passes between the outer condyle and the head of 

 the fibula. The tendon of Popliteus lies deep to it, between it and the tibia (Fig. 131), 

 and makes its exit from the capsule behind it. Some of its posterior fibres make an 

 arcuate band over the tendon, to join the condylar capsule. Its action, so far as the 

 knee joint is concerned, is similar to that of the internal lateral. 



The way in which these various structures are connected and covered in by the 

 different tissues concerned in forming the capsule is illustrated and described in Figs. 

 120 and 131. 



It is now possible to place these structures in position on the Tibia : they have 

 already been considered as they lie on the upper surface of the bone. 



In Fig. 131 the plan of the attachment of the capsule is shown, turning down in 

 front to reach the insertion of the patellar tendon. This encloses the triangular 

 surface A, on which is placed the infrapatellar pad and bursa. Observe that the 

 capsular line behind lies near the edge of the bone and turns forward by the popliteal 

 notch : here the proper capsular fibres are applied to the sides of the posterior crucial 

 ligament. 



F.A. 1 1 



