1186 SURGICAL AND TOPOGRAPHICAL AXATOMY 



but the posterior surface of the posterior crucial, which is connected by means of 

 fibro-areolar tissue to the front of the hganientuni ])OSticuni, and the lower portions 

 of both crucial ligaments, where they are united together, of course cannot receive a 

 complete covering from the membrane ' (Morris). From the above ligaments the 

 membrane is conducted, lining the lower part of the capsule and other ligaments, 

 to the semi-lunar cartilages, first over their upper surfaces to their free borders, and 

 then along their under surfaces to the tibia. Between the outer of these and the 

 upper and l^ack i)art of the tibia is a prolongation of the synovial mcm])rane to 

 facilitate the play of the popliteus tendon. Special folds, with their packing of fat, 

 the ligamenta alaria and mucosa, pass l)etween the femur and patella. 



The following bursae about the knee-joint must be remembered. Some, it 

 will be seen, are much more constant than others: — 



A. In front. — (1) One between the patella and skin, the bursa prepatellaris 

 (fig. 751); (2) a deeper one between the ligamentum patellae and the upper part of 

 the tibia; (3) between the skin and the lower part of the tubercle of the tibia. 

 This is not constant. 



B. On the inner side. — (1) One between the inner head of the gastrocnemius 

 and inner condyle, often extending between the above muscle and the semi-mem- 

 branosus. This is the largest of the burste about the knee-joint, and, after adult 

 life, usually communicates with the knee-joint; (2) one superficial to the internal 

 lateral ligament, between it and the tendon of the sartorius, gracilis, and semi- 

 tendinosus; (3) one beneath the ligament, between it and the tendon of the semi- 

 membranosus; (4) one between the inner tuberosity of the tibia and the semi-mem- 

 branosus; (5) one between the semi-membranosus and semi-tendinosus. Of the 

 above bursae, the first two alone are constant. The second and third are often one 

 bursa prolonged. 



C. On the outer side. — (1) One between the outer head of the gastrocnemius 

 and the condyle; (2) one superficial to the external lateral ligament between it 

 and the biceps tendon; (3) one under the ligament between it and the popliteus 

 tendon; (4) one between the popliteus tendon and the outer condyle of the femur. 

 This is usually a diverticulum from the synovial membrane. 



The following explanations may be given of an inflamed knee-joint usually 

 taking the flexed position: (1) By experimental injections, Braune found that the 

 capacity of the synovial sac reaches its maximum with a definite degree of flexion, 

 i.e. at an angle of twenty-five degrees. (2) As the same nerves supply the 

 synovial membrane and the muscles which act upon the joint, the flexors being 

 more powerful than the extensors, will help to explain the flexed position 

 (Hilton). 



Anastomoses around the front and sides of the knee-joint. — The most 

 im2)ortant of these take the form of three transverse arches. (1) The highest 

 passes through the quadriceps fibres just above the upper edge of the patella. It 

 is formed by a branch from the deep division of the anastomotica and one from 

 the superior external articular. The middle and lowest arches lie under the 

 ligamentum patellae. (2) The middle arch, formed by branches from the anasto- 

 motica and superior internal articular on the inner side, and the inferior external 

 articular, on the outer, runs in the fatty tissue close to the apex of the juitella. (3) 

 The lowest arch lies on the tibia just al:)ove its tulierele, and results from the 

 anastomosis of the recurrent tilnal and the inferior internal articular. Six arteries 

 thus take place in this series of anastomoses. 



POPLITEAL SPACE 



In flexion, th(> hollow of this space appears; in extension it is obliterated and 

 its boundaries are ill-defined, the only one now to be made out being the semi- 

 tendinosus and the l>iceps. 



Popliteal tendons. — When the knee is a little bent, and the foot rests 

 on tlie ground, the following can l)e made out: At the outer side, behind the 

 ilio-tibial band, and descending to the head of the fil)ula, is the tendon of the 

 biceps. Parallel and close to its inner border, the external popliteal nerve 



