304 ARTICULATIONS. 



elongated from before backwards, and broader behind than in front ; its convex 

 border is united to the internal lateral ligament, and to the head of the tibia, 

 by means of the coronary ligaments ; its anterior extremity, thin and pointed, 

 is firmly implanted into a depression in front of the inner articular surface of 

 the tibia ; its posterior extremity into the depression behind the spine, between 

 the attachment of the external cartilage and posterior crucial ligament. 



The External Semilunar Fibro-cartilage forms nearly an entire circle, covering 

 a larger portion of the articular surface than the internal one. It is grooved 

 on its outer side, for the tendon of the Popliteus muscle. Its circumference is 

 held in connection with the head of the tibia, by means of the coronary liga- 

 ments ; and its two extremities are firmly implanted in the depressions in front 

 and behind the spine of the tibia. These extremities, at their insertion, are 

 interposed between the attachments of the internal cartilage. The external 

 semilunar fibre-cartilage gives off from its anterior border a fasciculus, which 

 forms the transverse ligament. By its anterior extremity, it is continuous with 

 the anterior crucial ligament. Its posterior extremity divides into three slips ; 

 two of these pass upwards and forwards, and are inserted into the outer side of 

 the inner tuberosity of the tibia, one in front, the other behind the posterior 

 crucial ligament; the third fasciculus is inserted into the back part of the 

 anterior crucial ligament. 



The Transverse Ligament is a band of fibres, which passes transversely from 

 the anterior convex margin of the external semilunar cartilage to the anterior 

 extremity of the internal cartilage ; its thickness varies considerably in different 

 subjects. 



The Coronary Ligaments consist of numerous short fibrous bands, which con- 

 nect the convex border of the semilunar cartilages with the circumference of 

 the head of the tibia, and with the other ligaments surrounding the joint. 



The Synovial Membrane of the knee-joint is the largest and most extensive in 

 the body. Commencing at the upper border of the patella, it forms a large cul- 

 de-sac beneath the Extensor tendon of the thigh : this is sometimes replaced by 

 a synovial bursa interposed between the tendon and the front of the femur, 

 which in some subjects communicates with the synovial membrane of the knee- 

 joint, by an orifice of variable size. On each side of the patella, the synovial 

 membrane extends beneath the aponeurosis of the Yasti muscles, and more 

 especially .beneath that of the Vastus Internus; and, below the patella, it is 

 separated from the anterior ligament by a considerable quantity of adipose 

 tissue. In this situation it sends off a triangular prolongation, containing a few 

 ligamentous fibres, which extends from the anterior part of the joint below the 

 patella, to the front of the inter-condyloid notch. This fold has been termed 

 the lirjamentum mucosum. The ligamenta alaria consist of two fringe-like folds, 

 which extend from the sides of the ligamentum mucosum, upwards and outwards, 

 to the sides of the patella. The synovial membrane invests the semilunar fibro- 

 cartilages, and on the back part of the external one forms a cul-de-sac between 

 the groove on its surface, and the tendon of the Popliteus ; it is continued to 

 the articular surface of the tibia : surrounds the crucial ligaments, and the inner 

 surface of the ligaments which inclose the joint ; lastly, it approaches the con- 

 dyles of the femur, and from them is continued on to the lower part of the front 

 of the shaft. The pouch of synovial membrane between the extensor tendon 

 and front of the femur is supported, during the movements of the knee, by a 

 small muscle, the Subcrureus, which is inserted into it. 



The arteries supplying the joint are derived from the anastomotic branch of 

 the femoral, articular branches of the popliteal, and recurrent branch of the 

 anterior tibial. 



The Nerves are derived from the obturator, anterior crural, and external and 

 internal popliteal. 



Actions. The knee-joint allows of movements of flexion and extension, and 

 of slight rotation inwards and outwards. The complicated mechanism of this 



