148 ARTHROLOGY. 



arises from the external condyle of the femur, and passes over 

 the head of the tibia to the fibula ; a synovial bursa lies between 

 it and the tibia. It is separated from the capsular ligament by 

 the tendon of origin of the popliteus. The internal lateral arises 

 from the internal condyle of the femur, and is attached to the 

 intero-lateral aspect of the head of the tibia. 



Ca'psular Ligament. — This name is usually applied to a mem- 

 branous ligament enclosing the joint posteriorly, and attached to 

 the femur, tibia, lateral ligaments, and menisci. It is by some 

 called the posterior ligament. Anterior to this there is a pair 

 of membranes enclosing the joint antero-laterally. These are 

 generally described as the synovial membranes ; but as they are 

 considerably strengthened, and help to play the part of a capsular 

 ligament, it may be convenient to describe them as such. There- 

 fore if there is a complete capsular ligament investing the joint, 

 it is thickened posteriorly. 



The synovial apparatus is double, each side having its own 

 membrane, and between the two are the crucial ligaments of the 

 joint. Anteriorly, the synovial membranes contact that of the 

 femoro-patellar joint, and it is found that sometimes the synovial 

 cavities are continuous with that of the latter. A large quantity 

 of fat fills up the space between the capsules and the straight 

 ligaments of the patella. The motions of this joint are flexion 

 and extension, and a certain amount of rotation, permitted by 

 the presence of the discs. 



TIBIO-FIBULAR ARTICULATION. 



This small articulation is formed by the facets on the adjacent 

 surfaces of the tibia and fibula, and is a diarthrodial joint. The 

 ligaments are a strong caiosular one and the interossei, which 

 divide into superior and inferior ; the former being a small 

 bundle at the upper third of the fibula ; the latter consists of a 

 membranous expansion, extending from the middle to the distal 

 extremity of the fibula. Between the two interosseous parts 

 pass the chief artery and vein of the region, the anterior tibial. 

 A ligamentous cord extends downwards from the fibula to the 

 external malleolus of the tibia, " where this cord bifurcates and 

 unites with the two external lateral ligaments of the tarsal joint '* 

 {Rigot). Motion in this joint can hardly be said to exist. 



