REGION OF THE KNEE. 



537 



but toward the upper edge of the internal condyle the capsule is again thin and 

 effusions puff it out at that point. 



Internal Lateral Ligament. A band of the capsule to which the name internal 

 lateral ligament has been applied runs from beneath the adductor tubercle to the tibia 

 below the internal tuberosity; it is strengthened by fibres from the tendon of the 

 semimembranosus and has the internal articular vessels and nerves passing between 

 it and the tibia. It will be noted that it 

 lies toward the posterior portion of the 

 joint, hence it limits extension (Fig. 546). 



Externally the capsule has likewise 

 the fibrous expansion of the quadriceps 

 from the side of the patella and the 

 fascia lata. This latter is the strong 

 iliotibial band and goes downward to 

 insert into the outer tuberosity of the 

 tibia (Fig. 547). 



External Lateral Ligaments. 

 There are likewise two band-like liga- 

 ments on the outer side, the long and 

 short external lateral ligaments. The 

 long external lateral ligament arises from 

 a tubercle just below and in front of the 

 outer head of the gastrocnemius muscle. 

 It is about 5 cm. (2 in.) long and is 

 attached below to the fibula, anterior to 

 its styloid process. It is embraced on 

 each side by the split tendon of the 

 biceps. Beneath it pass the popliteus 

 tendon in its sheath and the inferior ex- 

 ternal articular vessels and nerve. Note 

 that this is likewise at the posterior por- 

 tion of the joint and therefore it too 

 limits extension. 



The short or posterior of the two 

 external lateral ligaments is often not to 

 be recognized as a distinct structure, it 

 passes from the styloid process of the 

 fibula over the popliteus tendon to blend 

 with the posterior capsular ligament on 

 the external condyle. The lateral liga- 

 ments check extension and outward ro- 

 tation of the tibia. 



Crucial Ligaments. These pass 

 from the tibia, the anterior being at- 

 tached in front of and the posterior be- 

 hind the spine, upward to the intercon- 

 dylar notch of the femur. The anterior 

 or external passes upward, outward, and 

 backward. The posterior or internal 

 passes upward, inward, and forward (Fig. 548) . They are never very lax in any position 

 of the joint, but the anterior is most tense in extension and the posterior in flexion. 

 The anterior tends to prevent displacement of the tibia forward and the posterior liga- 

 ment displacement of the tibia backward. The posterior crucial ligament blends with 

 the posterior capsule and in resecting the knee care should be taken in dividing this 

 ligament that the popliteal artery is not wounded. A ligamentous band runs from the 

 posterior crucial ligament to the external semilunar cartilage; it is called the ligament 

 of Wrisberg, The knee-joint in some of the lower animals is composed of two sepa- 

 rate joints, one for each condyle, and the crucial ligaments of man are simply the 

 remains of lateral ligaments when separate joints exist. They check inward rotation. 



FIG. 548. The crucial ligaments exposed by sawing off 

 the inner surfaces of the femur and tibia. 



