292 



THE ARTICULATIONS 



The nerve-supply comes from the great sciatic, femoral, and obturator sources. The 

 great sciatic gives off the tibial and common peroneal; the tibial sends two, sometimes three 

 branches — one with the medial articular artery; one with the inferior medial, and sometimes 

 one with the superior medial articular artery; the common peroneal gives a branch which accom- 

 panies the superior, and another which accompanies the inferior articular artery, and a recurrent 

 branch which follows the course of the anterior recurrent branch of the anterior tibial artery. 

 The femoral sends an articular branch from the nerve to the vastus lateralis; a second from the 

 nerve to the vastus medialis; and sometimes a thu-d from that to the vastus intermedins. Thus 

 there are three articular twigs to the knee derived from the muscular branches of the femoral. 

 The obturator by its deep division sends a branch through the adductor magnus on to the pop- 

 liteal artery, which enters the joint posteriorly. 



Fig. 324. — Sagittal Section of the Knee-joint. 

 (The bones are somewhat drawn apart.) 



Muscular fibres of quadriceps 

 femoris 



Extension of synovial sac of knee 

 upon femur 



Fatty tissue 

 Opening in synovial mem- 

 brane behind crucial 

 ligament leading into 

 inner half of joint 

 Synovial membrane re- 

 flected off crucial ligaments 

 Cut end of anterior crucial 



ligament 

 Posterior crucial ligament 



Oblique popliteal ligament 



Tendon of quadriceps femoris, 

 forming fibrous capsule of joint 



Patella 

 Pre-patellar bursa 



jT— Condyle of femur 



Cmedial) 



—Patellar synovial fold 



Fatty tissue between 

 ligamentum patella 

 and synovial sac 



Bursa beneath ligamentum 

 patellse 



Tibia 



Relations.— Anteriorly and at the sides the knee-joint is merely covered and protectediby 

 skin, fascia, and the tendinous expansions of the quadriceps extensor muscle. Laterally and 

 posteriorly it is crossed by the biceps tendon. Medially and posteriorly lie the sartorius and 

 the tendons of the gracili.s and semitendinosus muscles, rostcriorly it is in relation with the 

 poi)litoal vessels and nerves, tlic sotnimenibranosus, the two heads of the gastrocnemius, and the 

 plantaris. The tendon of the i)oplitcu8 pierces the capsule behind and medial to the biceps 

 tendon. 



The movements which occur at the knee-joint are flexion and extension, with some slight 

 amount of rotation in the bent j)osition. These movements are not so simple as the correspond- 

 ing ones at the elbow, for the knee is not a sinii)le hinge joint. The movements of rotation 

 instead of occurring between 1il)ia and fibula, as between radius and ulna, are movements of the 

 tibia with the fibula uf)on tlic; condyles of tlie femur. 



The knee dilTers from a true hinge joint, like the elbow or ankle, in the following par- 

 ticulars: — 



1. The points of contact of the femur with the tibia are constantly changing. Thus, m 



