240 THE ARTICULATIONS OF THE HORSE 
inches (ca. 5 em.); here it is thin. It is continued downward to form the sub- 
tarsal or check ligament, which unites with the deep flexor tendon about the mid- 
dle of the metatarsus. 
There are four synovial sacs: 1. The tibio-tarsal sac lubricates the proximal 
joint, and is much the largest and most important.! 2. The proximal intertarsal 
sac lines the joints formed by the tibial and fibular tarsal bones above, and the cen- 
tral and fourth tarsals below; it communicates in front with the tibio-tarsal sac. 
3. The distal intertarsal sac lubricates the joints formed between the central tarsal 
and the bones below and on either side. 4. The tarso-metatarsal sac lubricates 
Tuber calcis 
vA 
Medial malleolus ~ 
Long medial ligament ~~ 
Trochlea of tibial tarsal bone Plantar bqamere 
Dorsal ligament. — 
Mt. II] —___& = MEE 
i 
Fie. 252.—Ricut Hock Joint or Horse; Meprat View. Tue Capscie 18 REMOVED. 
1, 2, Branches of short part of medial ligament; 3, tarso-metatarsal ligament; 4, proximal tuberosity of tibial tarsal 
bone; 5, sustentaculum; 6, groove for deep flexor tendon; Mt. IJ, Mt. III, metatarsal bones. 
the joints formed between the tarsal and metatarsal bones, those between the 
proximal ends of the metatarsal bones, and those formed by the third tarsal with 
the bones on either side. 
Common Ligaments.—The lateral ligament (Lig. collaterale fibulare) consists 
of two distinct bands which cross each other. The long lateral ligament (Lig. 
collaterale laterale longum) is superficial; it arises on the posterior part of the lateral 
malleolus, is directed almost straight downward, and is attached to the fibular and 
fourth tarsal bones and the large and lateral small metatarsal bones. It forms a 
canal for the lateral extensor tendon. The short lateral ligament (Lig. collaterale 
1TIt is this part of the capsule which is chiefly involved in distention by excess of fluid in the 
joint cavity (as in ‘‘bog-spavin’’). 
