KNEE-JOINT 71 



medial and lateral ligaments, and some strong oblique bands at the 

 back; and all are connected by a capsule which encloses the joint 

 cavity. 



The synovial membrane is very extensive (Fig. 66) ; it covers 

 the crucial ligaments and semilunar cartilages. 



Motions. Flexion, extension, and very limited rotation of the 

 leg. 



Note. The patella cannot be drawn upward under any circumstances. 

 When the knee is flexed, it lies against the lower ends of the condyles, and in 

 kneeling the condyles rest upon it. The elasticity of the great muscles to 



Extension of synovial sac of knee 

 upon femur 



Tendon of quadriceps extensor, 

 forming fibrous capsule of joint 



Patella 



- Pre-patellar bursa 

 Condyle of femur (inner) 

 Ligamentum mucosum 



Fatty tissue 



Synovial membrane re- 

 flected off crucial liga- 

 ments 



Cut end of anterior cru- 

 cial ligament 

 Posterior crucial liga- 

 ment 



Fatty tissue between 

 ligamentum patellae 

 and synovial sac 



Bursa beneath ligamentum 

 patellae 



Tibia 



FIG. 66. INTERIOR OF KNEE-JOINT. (Morris.) 



which the patellar tendon belongs, allows very free motion and at the same 

 time keeps the patella always in place close to the condyles. 



Bursse. There are several small cavities called bursse, the use of which is 

 to prevent friction in the tissue outside the knee-joint. They usually com- 

 municate with the joint. The largest one is, however, subcutaneous, being 

 in front of the patella between it and the skin. (Fig. 66 and page 82.) 



