OF THE PHALANGES. 387 



VIII. Articulations of the Phalanges. 



The articulations of the phalanges are ginglymus joints. 



The ligaments are 



Plantar. Two Lateral. 



The arrangement of these ligaments is similar to those in the metatarso- 

 phalangeal articulations ; the extensor tendon supplies the place of a posterior 

 ligament. 



Actions. The only movements permitted in the phalangeal joints are flexion 

 and extension : these movements are more extensive between the first and second 

 phalanges than between the second and third. The movement of flexion is very 

 considerable, but extension is limited by the anterior and lateral ligaments. 



Surface Form. The principal joints which it is necessary to distinguish, with regard to the 

 surgery of the foot, are the medio-tarsal and the tarso-metatarsal joints. The joint between the 

 astragalus and the navicular is best found by means of the tubercle of the navicular bone, for 

 the line of the joint is immediately behind this process. If the foot is grasped and forcibly 

 extended, a rounded prominence, the head of the astragalus, will appear on the inner side of 

 the dorsum in front of the ankle-joint, and if a knife is carried downward, just in front of this 

 prominence and behind the line of the navicular tubercle, it will enter the astragalo-navicular 

 joint. The calcaneo-cuboid joint is situated midway between the external malleolus and the 

 prominent end of the fifth metatarsal bone. The plane of the joint is in the same line as that 

 of the astragalo-navicular. The position of the joint between the fifth metatarsal bone and the 

 cuboid is easily found by tbe projection of tbe fifth metatarsal bone, which is the guide to it. 

 The direction of the line of tbe joint is very oblique, so that, if continued onward, it would 

 pass through the head of the first metatarsal bone. The joint between the fourth metatarsal 

 bone and the cuboid and external cuneiform is the direct continuation inward of the previous 

 joint, but its plane is less oblique ; it would be represented by a line drawn from the outer side 

 of the articulation to the middle of the first metatarsal bone. The plane of the joint between 

 the third metatarsal bone and the external cuneiform is almost transverse. It would be repre- 

 sented by a line drawn from the outer side of tbe joint to the base of the first metatarsal bone. 

 The tarso-metatarsal articulation of tbe great toe corresponds to a groove which can be felt by 

 making firm pressure on the inner side of the foot one inch in front of the tubercle on the 

 navicular bone ; and the joint between the second metatarsal bone and the middle cuneiform is 

 to be found on the dorsum of tbe foot, half an inch behind the level of tbe tarso-metatarsal 

 joint of the great toe. Tbe line of the joints between the metatarsal bones and the first 

 phalanges is alxmt an inch behind the webs of the corresponding toes. 



