276 



THE ARTICULATIONS. 



Femur 



the Gastrocnemius, Plantaris, and Popliteus muscles. It passes in front of, but is 

 inseparably connected with, the posterior ligament. 



The Crucial are two interosseous ligaments of considerable strength situated 



in the interior of the joint, nearer its posterior 

 than its anterior part. They are called crucial 

 because they cross each other somewhat like 

 the lines of the letter X ; and have received 

 the names anterior and posterior, from the 

 position of their attachment to the tibia. 



The Anterior, or External Crucial Liga- 

 ment (Fig. 185), is attached to the depres- 

 sion in front of the spine of the tibia, being 

 blended with the anterior extremity of the 

 external semilunar fibro-cartilage, and, pass- 

 ing obliquely upward, backward, and out- 

 ward, is inserted into the inner and back 

 part of the outer condyle of the femur. 



The Posterior, or Internal Crucial Liga- 

 ment, is stronger, but shorter and less ob- 

 lique in its direction, than the anterior. It 

 is attached to the back part of the depres- 

 sion behind the spine of the tibia, to the 

 popliteal notch, and to the posterior extrem- 

 ity of the external semilunar fibro-cartilage ; 

 and passes upward, forward, and inward, to 

 be inserted into the outer and fore part of the 

 inner condyle of the femur. It is in relation, 

 in front, with the anterior crucial ligament ; 

 behind, with the capsular ligament. 



The Semilunar Fibro-cartilages (Fig. 186) 

 are two crescentic lamellae which serve to 

 naiFig G am" ightknee " Joint ' showillg inter ' deepen the surface of the head of the 



tibia, for articulation with the condyles of 



the femur. The circumference of each cartilage is thick, convex, and attached to 

 the inside of the capsule of the knee ; the inner border is thin, concave and 



free. Their upper surfaces 

 are concave, and in relation 

 with the condyles of the 

 femur; their lower surfaces 

 are flat, and rest upon the 

 head of the tibia. Each car- 

 tilage covers nearly the outer 

 two-thirds of the correspond- 

 ing articular surface of the 

 tibia, leaving the inner third 

 uncovered ; both surfaces are 

 smooth and invested by syno- 

 vial membrane. 



The Internal Semilunar 

 Fibro-cartilage is nearly sem- 

 icircular in form, a little 

 elongated from before back- 

 ward, and broader behind than in front ; its anterior extremity, thin and pointed, 

 is attached to a depression on the anterior margin of the head of the tibia, in 

 front of the anterior crucial ligament ; its posterior extremity is attached to the 

 depression behind the spine, between the attachments of the external semilunar 

 fibro-cartilage and the posterior crucial ligaments. 



FIG. 186. Head of tibia, with semilunar cartilages, etc. Seen from 

 above. Right side. 



