258 



THE A R TIC I 'LA TIOXS 



tibia, and moving' with the tibia upon the femur. They somewhat deepen the tibial 

 articuUir surfaces, and are dense and compact in structure, becoming looser and 

 more fil)rous near their extremities, where they are firmly fixed in front of and 

 behind the spine of the tibia. The circumferential border of each is convex, thick, 

 and somewhat loosely attached to the borders of the tuberosities of the tibia by the 

 coronary ligaments, and the reflexion of the syno\dal membrane. The inner border 

 is concave, thin, and free. lialf^an inch (l-o cm.) broad at the widest part, they 

 taper somewhat towards their extremities, and cover rather less than two-thirds of 

 the articular facets of the tibia. Their upper surfaces are slightly concave, and tit 

 on to the femoral condyles, while the lower are flat and rest on the head of the 

 tibia; both surfaces are smootli and covered by synovial membrane. 



The external semilunar cartilage (fig. 247) is nearly circular in form and less 

 firmlv fixed than the internal, and consequently slides more freely upon the tibia. 



Fig. 248. — Anterior View of the Knee-joint, showing the Synovial Ligaments. 

 (Anterior portion of capsule with the extensor teudou thrown downwards.) 



Posterior crucial 



Ijigamentum mucosum 



Alar ligament 



Synovial pouch under tendon 

 of quadriceps extensor 



Alar ligament 



Its anterior cornu is attached to a narrow depression along the outer articular facet, 

 just in front of the external tubercle of the tibial spine, close to, and on the outer 

 side of, the anterior crucial ligament; a small slip from the cornu is often fixed to 

 the til)ia in front of the crucial ligament. The posterior cornu is firmly attached to 

 the tibia behind the external tubercle of the spine, blending with the posterior 

 crucial ligament, and giving off a well-marked fasciculus, which runs up along the 

 anterior border of the ligament to be attached to the femur (ligament of Wrisberg). 

 It also sends a narrow slip into the back part of the anterior crucial ligament. 



Its outer border is grooved towards its posterior part by the poplitem tendon, 

 which is held to it by fibrous tissue and synovial meml)rane', and separates it from 

 the external lateral ligament. From its anterior border is given oft' the transverse 

 ligament. 



The internal semilunar cartilage (lig. 247) is a segment of a larger circle than 



