92 TOPOGRAPHICAL ANATOMY OF 



thinner and more roomy, and extends for some distance between the 

 second phalanx and the deep flexor tendon. For surgical reasons it is 

 important to note that there is a small diverticulum of the joint 

 capsule, in contact with the deep surface of each cartilage of the third 

 phalanx immediately behind a collateral ligament. 



The stout collateral ligaments (ligamentum collaterale mediale : 

 laterale) pass from the distal end of the second phalanx to the 

 depressions on each side of the extensor process of the third 

 phalanx. 



Strong, but elastic, collateral sesamoidean ligaments (ligamentum 

 sesamoideum collaterale mediale : laterale) arise mainly from the 

 borders of the second phalanx, but some fibres (blended with the 

 collateral ligament of the preceding joint) can be traced to the distal 

 end of the first phalanx. The collateral ligaments end on the upper 

 (proximal) border of the sesamoid bone; some fibres being attached 

 to the deep face of the cartilage of the third phalanx and to the angle 

 of the phalanx itself. 



