TIBIO-FIBULAR ARTICULATION — THE HOCK JOINT 



199 



ridge. During flexion, which is aeconipanied by sHglit inward rotation of the leg, the condyles 

 of the femur and the semilunar cartilages glide backward on the tilna; the movement of the ex- 

 ternal condyle and cartilage is greater than that of the inner one. In extreme tlexidu tiie patellar 

 and posterior crucial ligaments are ten.se; the other ligaments are rela.xed. The movement of the 

 patella is gliding with coaptation, t. c, different parts of the opposing articular surfaces come into 

 contact successively. Onh' a narrow transverse strip (ca. 1.5 to 2 cm. wide) of the patella is in 

 contact with the trochlea at a time. 



TIBIO-FIBULAR ARTICULATION 



Th(> head of t\w fibula articulates with a ("rcsccntic facet just below the outer 

 margin of the external condyle of the tibia. The joint capsule is strong and close. 

 The shaft of the fibula is attached to the external border of the tibia by the inter- 

 osseous membrane of the lefj (Meinl)rana interossea cruris); this is perforated 

 ai)out an inch from its proximal end by an ojKMiinf!; which transmits the anterior 

 tii)ial vessels to the front of the til)ia. A fil)rous cord usually extenils from the 

 distal end of the shaft of the fibula to the external malleolus. The latter is the 

 distal end of the fil)ula which has fii.sed with the tibia. No ai)preciable movement 

 occurs in this joint. 



ExUrndl 

 Idlcrtil 

 {.•ihort) , 

 lif/nmciit ^ 

 Trochlea of 

 tihUd tar.siil 

 Dor-siil lif/d- ■ 

 nicnt 



■ PI I in Id r 

 liijdment 



Smdll 



vutatarsal 



bone 



Pldiilar 

 U(jdinvnl 



Small . --- :A. ' 

 7neta- \ 



tarsal 

 bone 



Jntirndl 

 Idtcral 

 :ss- . (shorl) 

 Uqanunt 

 Trochlea of 

 tibial tarsal 

 " Dorsal 

 ligament 



Fig. ItlL'. — Lkft Hock Joint of Horsk, Extkrnal Fir,. Ifi."?.— Left Hock Joint op Horse, Internal 



View. View. 



2/, Tibia; ^4, tuber calci.s; ^.5, large inetatar.sal bone; .^7, long external lateral ligament; 5/, long internal lateral 

 ligament. (After Ellenberger-Baum, Anat. fiir Kiinstler.) 



THE HOCK JOINT 



This is a composite joint made up of a number of articulations (Articulationes 

 tarsi). These are: (1) The ti))io-tarsal articulation; (2) the intertarsal articula- 

 tions; (3) the tarso-metatarsal articulation. 



The tibio-tarsal articulation (xVrticulatio talo-cruralis) is a typical ginglymus 

 formed by the trochlea of the tibial tarsal bone (astragalus or talus) and the cor- 

 responding surface of the distal end of the ti})ia. The ridges and grooves of these 

 surfaces are directed obliquely forward and outward at an angle of about 12° to 15°, 

 with a sagittal plane. The trochlear surface is about twice as extensive as that 

 on the tibia, and its ridges have a spiral curvature. The other articulations are 



