REGIONAL ANATOMY 15 



The Lateral Ligaments. — These are large and thick, an 

 outer and an inner, running obliquely from above down- 

 wards and backwards. Each is inserted superiorly into 

 the lateral tubercle of the lower end of the first phalanx, 

 and inferiorly to the side of the second phalanx, their most 

 inferior fibres becoming finally fixed to the extremities of 

 the navicular bone, where they form the postero-lateral 

 ligaments of the pedal articulation. In front of the joint 

 the extensor pedis plays the part of an additional ligament. 



The Synovial Membrane. — This is limited in front by the 

 tendon of the extensor pedis, on each side by the lateral 

 ligaments of the joint, and behind by the glenoid fibro- 

 cartilage. At this point it is prolonged upwards as a pouch 

 behind the lower extremity of the first phalanx. 



The Articulation of the Second Phalanx with the 

 Third, the Pedal, or the Coffin Joint. — This also is an 

 imperfect hinge-joint, permitting only of flexion and exten- 

 sion, which movements are more restricted than in the 

 previous articulation. Three bones enter into its forma- 

 tion : the second phalanx, the third phalanx, and the 

 navicular bone. The lower articulatory surface is formed 

 by the third phalanx and the navicular bone combined. 

 To effect this the navicular is closely and firmly attached 

 to the third phalanx by an interosseous ligament. The 

 two bones, as one, are then connected to the second phalanx 

 by four lateral ligaments, an anterior and a posterior on 

 each side. 



The Interosseous Ligament consists of extremely short 

 fibres running from the extensively grooved portion of the 

 anterior surface of the navicular bone to become attached 

 to the OS pedis immediately behind its articular surface. 



The Ante fo -lateral Ligaments are attached by their 

 superior extremities to the lateral surfaces of the second 

 phalanx, and by their inferior extremities into the depres- 

 sions on either side of the pyramidal process of the 

 OS pedis. 



The Postero-lateral lAgaments. — As mentioned when 

 describing the first interphalangeal articulation, these are 



