152 TIBIOFIBULAR ARTICULATIONS. 



Besides the proper ligaments of the articulation, the joint is pro- 

 tected on its anterior part by the fascia lata, which is thicker upon the 

 outer than upon the inner side, by a tendinous expansion from the 

 vastus internus, and by some scattered ligamentous fibres which are 

 inserted into the sides of the patella. 



Actions. The knee-joint is one of the strongest of the articulations 

 of the body, while at the same time it admits of the most perfect de- 

 gree of movement in the directions of flexion and extension. During 

 flexion the articular surface of the tibia glides forward on the condyles 

 of the femur, the lateral ligaments, the posterior, and the crucial liga- 

 ments are relaxed, while the ligamentum patellae being put upon the 

 stretch, serves to press the adipose mass into the vacuity formed in the 

 front of the joint. In extension all the ligaments are put upon the 

 stretch with the exception of the ligamentum patellae. When the 

 knee is semi-flexed, a partial degree of rotation is permitted. 



3. Articulation between the Tibia and Fibula. The tibia and 

 fibula are held firmly connected by means of seven ligaments, viz. 



Anterior, J , 

 Posterior, f ab 



Interosseous membrane, 

 Interosseous inferior, 



Anterior, K , 

 Posterior, J be 

 Transverse. 



The anterior superior ligament is a strong fasciculus of parallel 

 fibres passing obliquely downwards and outwards from the inner 

 tuberosity of the tibia, to the anterior surface of the head of the 

 fibula. 



The posterior superior ligament is disposed in a similar manner 

 upon the posterior surface of the joint. 



Within the articulation there is a distinct synovial membrane which 

 is sometimes continuous with that of the knee-joint. 



The interosseous membrane or superior interosseous ligament is a 

 broad layer of aponeurotic fibres which pass obliquely downwards and 

 outwards, from the sharp ridge on the tibia, to the inner edge of the 

 fibula and are crossed at an acute angle by a few fibres passing in the 

 opposite direction. The ligament is deficient above, leaving a con- 

 siderable interval between the bones, through which the anterior tibial 

 artery takes its course forwards to the anterior aspect of the leg, and 

 near its lower third there is an opening for the anterior peroneal artery 

 and vein. 



The interosseous membrane is in relation, in front, with the tibialis 

 anticus, extensor longus digitorum, and extensor proprius pollicis 

 muscle, with the anterior tibial vessels and nerve, and with the ante- 

 rior peroneal artery ; and behind with the tibialis posticus, and flexor 

 longus digitorum muscle, and with the posterior peroneal artery. 



