TIBIO-FIBULAR. 227 



present two flat oval surfaces covered with, cartilage, and connected together by 

 the following ligaments. 



o 



Anterior Superior Tibio-fibular. 

 Posterior Superior Tibio-fibular. 



The Anterior Superior Ligament (fig. 141) consists of two or three broad and 

 flat bands, which pass obliquely upwards and inwards, from the head of the fibula 

 to the outer tuberosity of the tibia. 



The Posterior Superior Ligament is a single thick and broad band, which 

 passes from the back part of the head of the fibula to the back part of the outer 

 tuberosity of the tibia. It is covered in by the tendon of the Popliteus muscle. 



A Synovial Membrane lines this articulation. It is occasionally continuous 

 with that of the knee-joint at its upper and back part. 



2. MIDDLE TIBIO-FIBULAR ARTICULATION. 



An interosseous membrane extends between the contiguous margins of the tibia 

 and fibula, and separates the muscles on the front from those on the back of the 

 leg. It consists of a thin aponeurotic lamina composed of oblique fibres, which 

 pass between the interosseous ridges on the two bones. It is broader above than 

 below, and presents at its upper part a large oval aperture for the passage of the 

 anterior tibial artery forwards to the anterior aspect of the leg ; and at its lower 

 part, an opening for the passage of the anterior peroneal vessels. It is continuous 

 below with the inferior interosseous ligament ; and is perforated in numerous parts 

 for the passage of small vessels. It is in relation in front with the Tibialis anticus, 

 Extensor longus digitorum, Extensor proprius pollicis, Peroneus tertius, and the 

 anterior tibial vessels and nerve ; behind, with the Tibialis posticus and Flexor 

 longus pollicis. 



3. INFERIOR TIBIO-FIBULAR ARTICULATION. 



This articulation is formed by the rough convex surface at the inner side of 

 the lower end of the fibula, being connected with a similar rough surface on 

 the outer side of the tibia. Below, to the extent of about two lines, these surfaces 

 are smooth and covered with cartilage, which is continuous with that of the ankle- 

 joint. Its ligaments are 



Inferior Interosseous. Posterior Inferior Tibio-fibular. 



Anterior Inferior Tibio-fibular. Transverse. 



The Inferior Interosseous Ligament consists of numerous short, strong fibrous 

 bands, which pass between the contiguous rough surfaces of the tibia and fibula, 

 constituting the chief bond of union between these bones. It is continuous, above, 

 with the interosseous membrane. 



The Anterior Inferior Ligament (fig. 144) is a flat triangular band of fibres, 

 broader below than above, which extends obliquely downwards and outwards 

 between the adjacent margins of the tibia and fibula on the front aspect of the 

 articulation. It is in relation, in front, with the Peroneus tertius, the aponeurosis 

 of the leg, and the integument ; behind, with the inferior interosseous ligament, 

 and lies in contact with the cartilage covering the astragalus. 

 ^ The Posterior Inferior Ligament, smaller than the preceding, is disposed in a 

 similar manner on the posterior surface of the articulation. 



The Transverse Ligament is a long narrow band of ligamentous fibres, con- 

 tinuous with the preceding, passing transversely across the back of the joint, 

 from the external malleolus to the tibia, a short distance from its malleolar process. 

 This ligament projects below the margins of the bones, and forms part of the 

 articulating surface for the astragalus. 



The Synovial Membrane lining the articular surfaces is derived from that of 

 the ankle-joint. 



