306 ARTICULATIONS 



quently, be subdivided into three sets. 1. Superior Tibio-fibular articulation. 

 2. Middle Tibio-fibular articulation. 3. Inferior Tibio-fibular articulation. 



1. SUPERIOR TIBIO-FIBULAR ARTICULATION. 



This articulation is an arthrodial joint. The contiguous surfaces of the bones 

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

 the following ligaments: 



Anterior Superior Tibio-fibular. 

 Posterior Superior Tibio-fibular. 



The Anterior Superior Ligament (Fig. 208) 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 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 of the inner side 

 of the lower end of the fibula, 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. The ligaments of this joint 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, and constitute the chief bond of union between the bones. This liga- 

 ment is continuous, above, with the interosseous membrane. 



The Anterior Inferior Ligament (Fig. 211) 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 aponou- 

 rosis 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, continuous with the pre- 



