120 



THE SKELETON OF THE HORSE 



The Tibial Tarsal Bone 

 The tibial tarsal bone (Os tarsi tibiale)i is the medial bone of the proximal row. 

 It is extremely irregular in form, but may be considered as offering six surfaces for 

 description. 



The proximal and dorsal surfaces are continuous, and form a trochlea (Troch- 

 lea tali) for articulation with the distal end of the tibia. The trochlea consists 



of two oblique ridges with a deep groove 

 between them; these curve spirally for- 

 ward, downward, and outward, forming 

 an angle of 12 to 15 degrees with a sagittal 

 plane . There is usually a shallow synovial 

 fossa in the groove. The distal surface is 

 convex from before backward, and most 

 of it articulates with the central tarsal; 

 laterally it has an oblique facet for the 

 fourth tarsal, and a non-articular groove 

 cuts into the surface to its middle. The 

 plantar surface (Fades plantaris) is ob- 

 lique and extremely irregular; it presents 

 four facets for articulation with the fibular 

 tarsal bone; the facets are separated by 



Trochlea 



Fig. 105. — Right Tahsits axd Proximal Past of 

 Metatarsi's of Horse; Lateral View. 

 Tt, Tibial tarsal (trochlea); Tf, fibular tarsal 

 (body); Tc, central tarsal; TS, third tarsal; T4, 

 fourth tarsal; 1, depression for attachment of lateral 

 ligament; 2, processus cochlearis; 3, prominence for 

 attachment of lateral ligament; 4, groove for great 

 metatarsal artery; 5, tuber calcis; Mi. Ill, IV, meta- 

 tarsal bones. Arrow points to vascular canal. 



Fig. 106. — Right Tibial Tarsal Boxe of Horse; Plan- 

 tar ^'IEW. 

 1-4, Facets for articulation with fibular tarsal; 5, fossa; 

 6, distal tuberosity; 7, proximal tuberosity. 



rough excavated areas, and the largest 

 fossa (Sulcus tali) forms with a corres- 

 ponding one on the fibular tarsal a cavity 

 termed the sinus tarsi. The medial surface bears on its distal part a large tuber- 

 osity and on its proximal part a small one for the attachment of the medial liga- 

 ment of the hock joint. The lateral surface is smaller than the medial, and is 

 marked by a wide rough fossa in which the lateral ligament is attached. 



The Fibular Tarsal Bone 

 The fibular tarsal bone (Os tarsi fibulare)- is the largest bone of the hock. 



It 



is elongated, flattened from side to side, and forms a lever for the muscles which 

 1 Also termed the astragalus or talus. ^ Also termed the calcaneum or os calcis. 



