TARSO-METATARSAL JOINTS 307 



The long plantar ligament (fig. 336) is a strong, dense band of fibres which is attached pos- 

 teriorly to the whole of the inferior surface of the calcaneus between the posterior tubercles and 

 the rounded eminence (the anterior tubercle) at the anterior end of the bone. Most of its fibres 

 pass directly forward, and are fixed to the lateral two-thirds or more of the oblique ridge behind 

 the peroneal gi'oove on the cuboid, while some pass further forward and medially, expanding 

 into a broad layer, and are inserted into the bases of the second, third, fourth, and medial half 

 of the fifth metatarsal bones. This anterior expanded portion completes the canal for the 

 peroncus longus tendon, and from its under surface arise the oblique adductor hallucis and the 

 flexor quinti digiii brevis muscles. 



The plantar calcaneo-cuboid (short plantar) (fig. 336) is attached to the rounded eminence 

 (anterior tubercle) at the anterior end of the under surface of the calcaneus, and to the bone in 

 front of it, and then takes an oblique course forward and medialh^ and is attached to the whole 

 of the depressed inferior surface of the cuboid behind the obhque ridge, except its lateral angle. 

 It is strongest near its lateral edge, and is formed by dense strong fibres. 



The synovial membrane is distinct from that of any other tarsal joint. 



The arterial supply of the medio-tarsal joints is from the anterior tibial, from the tarsal 

 and metatarsal branches of the dorsalis pedis, and from the plantar arteries. 



The nerve-supply of the medio-tarsal joints is from the lateral division of the deep 

 peroneal, and occasionally from the superficial peroneal or lateral plantar. 



Relations. — On the dorsal aspect of the mid-tarsal joint lie the tendons of the tibialis 

 anterior, extensor hallucis longus, extensor digitorum longus, and peroneus tertius, the muscular 

 part of the extensor digitorum brevis, the dorsalis pedis artery, and the anterior tibial nerve. 

 On its plantar aspect are the tendons of the flexor digitorum longus and hallucis longus, quadratus 

 plantae (accessorius), and the medial and lateral plantar vessels and nerves. It is crossed later- 

 ally by the tendons of the peroneus longus and brevis and medially by the tendon of the tibialis 

 posterior. 



The movements which take place at the medio-tarsal joints are mainly flexion and extension, 

 with superadded side-to-side and rotatory movements. Flexion at these joints is simultaneous 

 with extension of the ankle, and vice versa. Flexion and extension do not take place upon a 

 transverse, but round an oblique, axis which passes from the medial to the lateral side, and some- 

 what backward and downward through the talus and calcaneus. 



Combined with flexion and extension is also some rotatory motion round an antero-posterior 

 axis which turns the medial or lateral border of the foot upward. There is also a fair amount 

 of side-to-side motion whereby the foot can be inclined medially (i. e., adducted) or laterally 

 (i. e., abducted). 



These movements of the medio-tarsal joint occur in conjunction with those of the ankle 

 and talo-calcaneal joints. Rotation at the talo-calcaneal joint is, however, round a vertical 

 axis in a horizontal plane, and so turns the toes medially or laterally; whereas at the medio- 

 tarsal union the axis is antero-posterior and the medial or lateral edge of the foot is turned up- 

 ward. ■ Gliding at the talo-calcaneal joint elevates or depresses the edge of the foot, while at 

 the medio-tarsal it adducts or abducts the toes without altering the relative position of the cal- 

 caneus to the talus. 



Thus flexion at the medio-tarsal joint is associated with adduction and medial rotation 

 of the foot, occurring simultaneously with extension of the ankle; and extension at the medio- 

 tarsal joint is associated with abduction and lateral rotation, occurring simultaneously with 

 flexion of the ankle. 



Flexion and medial rotation are far more free than extension and lateral rotation, which 

 latter movements are arrested by the ligaments of the sole as soon as the foot is brought into the 

 position in which it rests on the ground. 



Although the talo-navicular is a baU-and-socket joint, yet, owing to the union of the 

 navicular with the cuboid, its movements are limited by the shape of the calcaneo-cuboid joint; 

 this latter being concavo-convex from above downward, prevents rotation round a vertical axis, 

 and also any side-to-side motion except in a direction obhquely downward and mediallj^, and 

 upward and laterally. This is also the direction of freest movement at the talo-navicular joint. 

 Movement is also Limited by the ligamentous union of the calcaneus with the navicular. The 

 twisting movement of the foot, such as tm*ning it upon its medial or lateral edge, and the increase 

 or diminution of the arch, take place at the tarsal joints, especially the medio-tarsal and talo- 

 calcaneal articulations. Here too those changes occur which, owing to paralysis of some mus- 

 cles or contraction of others, result in talipes equino-varus, or valgus. 



Muscles which act on the mid-tarsal joint. — Medial rotators. — Tibialis anterior and posterior 

 acting simultaneously; they are aided by the flexor digitorum longus and flexor hallucis longus. 

 Lateral rotators. — The peronei longus, brevis, and tertius, acting simultaneously. They are 

 aided by the extensor digitorum longus. 



6. THE TARSO-METATARSAL ARTICULATIONS 



There may be said to be three articulations between the tarsus and metatarsus, 

 viz. : — 



(a) The medial, between the first cuneiform and first metatarsal bones. 



(6) The intermediate, between the three cuneiform and second and third 

 metatarsal bones. 



(c) The lateral, or cubo-metatarsal, between the cuboid and fourth and fifth 

 metatarsal bones. 



