JOINTS OF THE FOOT 437 



joint formed by the head of the talus, the navicular, the sus- 

 tentaculum tali, the plantar calcaneo-navicular ligament, the 

 navicular part of the bifurcate ligament and talo-navicular 

 ligament. (4) The cavity of the naviculo-cuneiform articula- 

 tion, which is prolonged forwards between the cuneiforms, 

 and also between the cuboid and third cuneiform bones; 

 that cavity extends beyond the tarsus, and is continuous 

 with the cavity between the second and third metatarsal 

 bones and the tarsus, as well as with the cavities of the 

 joints between the bases of the second, third, and fourth 

 metatarsal bones. 1 (5) A separate cavity lies between the 

 first metatarsal and the first cuneiform. (6) A distinct 

 cavity for the articulations between the cuboid and the 

 lateral two metatarsal bones ; this is prolonged distally into 

 the joint between the bases of these two metatarsals. 



Metatarso-phalangeal and Interphalangeal Joints. The 

 metatarso-phalangeal and interphalangeal joints of the foot 

 are constructed on a plan which is practically identical with 

 that met with in the cases of the corresponding joints of the 

 hand. In the cases of the metatarso-phalangeal joints the 

 slightly cupped bases of the first phalanges articulate with the 

 rounded heads of the metatarsal bones. The joints so formed 

 are of the condyloid variety and allow flexion, extension, 

 abduction, adduction, and circumduction. The interphalan- 

 geal joints, on the other hand, are hinge joints, which permit 

 only flexion and extension. In them there are two cup- 

 shaped depressions at the proximal end of the distal bone, 

 which fit against the condyles of the trochlear surface of the 

 distal end of the proximal bone. In both the metatarso- 

 phalangeal joints and the interphalangeal joints the articular 

 surfaces on the distal bones of the joints are limited, strictly, 

 to the proximal ends of the bones, but the articular surfaces 

 on the distal ends of the proximal bones are more extensive 

 and are prolonged for a considerable distance on the plantar 

 surface of the distal end of each bone. The result of this 

 arrangement is that when the joints are extended a consider- 

 able part of the convex articular surface of the proximal bone 

 rests upon the plantar accessory ligament of the joint capsule, 



1 The lateral interosseous tarso-metatarsal ligament, which passes from 

 the third cuneiform bone (frequently from the cuboid bone) to the base of 

 the fourth metatarsal bone, separates the cavity between the fourth and fifth 

 metatarsal bones and the cuboid from the general tarsal articular cavity. 



