THE KNEE-JOINT. 



407 



the fibrous layers from the tendon of the quadriceps over the lower part of the bone 

 in eighty per cent. (3) A large and constant bursa lies on the smooth anterior 

 surface of the tubercle of the tibia beneath the ligamentum patellae, which is inserted 

 into the lower part. It extends upward to about the level of the top of the tibia, 

 from which it is separated by the fat below the knee. It practically never communi- 

 cates with the knee-joint. As the tendon before it is inserted obliquely, descend- 

 ing lower on the outer side, the shape of the bursa is roughly triangular. The 

 greatest diameter is the transverse one at the top, the outer border is not quite so 

 long, and the inner about half the length of the outer. The breadth is from 3 to 4 

 centimetres, the outer border from 2.5 to 4, and the inner from 1.5 to 2.5 centi- 

 metres. (4) A subcutaneous bursa is often found over the tuberosity of the tibia 



Fig. 422. 



Posterior crucial ligament 



Anterior crucial ligament 

 Capsule 



Internal semilunar 

 cartilage 



Fascia lata 



Fascia lata 



External semilunar 

 I cartilage 



Capsule 



Frontal section through middle of right knee-joint. Seen from behind. 



and (5) another over the ligament of the patella. At the back of the knee there are 

 several bursae. (6) The largest is that beneath the inner head of the gastrocne- 

 mius (Fig. 426), which later in life often connects with the joint. It is usually 

 prolonged between the gastrocnemius and the tendon of the semimembranosus. 

 (7) A bursa is commonly found between the long lateral ligament and the tendon 

 of the popliteus as it passes beneath it, and another between the ligament and the 

 tendon of the biceps. 



The relations of the tendon of the poplitetis muscle are so important as to re- 

 quire a separate description. The muscular belly is usually separated from the back 

 of the tibia, near the top, by a prolongation of the capsule between the tibia and the 

 back of the external semilunar cartilage, which is described by some as a bursa com- 

 municating with the joint. According to either view, there is a deficiency of the 

 coronary ligament at this point. The muscle is connected beyond this with the 

 outer side of the external semilunar cartilage. Passing above this, it becomes a part 



