FETLOCK JOINT 417 



extend from the base of each sesamoid bone to the tubercle which exists 

 on the superior side of the os coronse. On their internal faces they are 

 lined with synovial membrane. 



The inter-sesamoideal liyament consists of fibro-cartilaginous substance, 

 which runs from the posterior part of one sesamoid bone to that of the 

 other, spreading over the external surface of the outer, and internal surface 

 of the inner bone. It is composed of the fibro-cartilaginous substance in 

 which the ossa sesamoidea were originally developed. This mass of fibrous 

 matter, in common with the posterior and internal faces of the two bones, 

 forms the smooth pulley-Hke groove over which the flexor tendons play, 



2. The ligaments connectitKj the cannon-hone to the pastern (or, in scientific 

 language, the metacarpus to tlie os suffraginis) are three, namely, two 

 lateral and a capsular. 



Each lateral ligament consists of two bundles of fibres, one superficial and 

 one deep-seated, firmly united together at their adjacent surfaces. The 

 superficial arises from a projection on the infero-lateral part of the large 

 metacarpal bone, just above the condyloid surface. It descends vertically, 

 so as to terminate on the lateral parts of the superior extremity of the os 

 suffraginis. The deep-seated one is attached strongly to the excavation on 

 the lateral surfaces of the anterior extremity of the large metacarpal bone, 

 and directs its course from the ossa sesamoidea to the superior extremity of 

 the OS suff'raginis, where it is fixed, by mixing its fibres with the lateral 

 sesamoideal ligaments. 



The cai^sular ligament is a very resisting membranous expansion, which is 

 attached to the edges of the cartilaginous articular surfaces of the bones 

 composing this joint. It is internally lined with synovial membrane. 



IVie suspensory ligament, which should be carefully studied on account of 

 the numerous accidents to which it is liable, is attached to all four of tl e 

 bones entering into this joint, and may be described as being composed of a 

 strong band of white fibrous tissue, sometimes having intermixed a few 

 bundles of muscular tissue. It is thin and comparatively weak towards the 

 knee, but as it approaches the fetlock joint, it almost equals the back 

 sinews in substance, and its volume and wiriness to the touch may be taken 

 as some test of the power of any particular leg in resisting a " break down." 

 Occupying the space between the two small metacarpal bones, and lying 

 close against the large metacarpal, it arises from the posterior common 

 ligament of the knee joint, from a projection on the back of the large 

 metacarpal bone just below it, and from the inner sides of the heads of the 

 small metacarpals. Descending thence close to the large metacarpal bones, 

 it splits into two strong bands, each of which is attached to the upper edge 

 of the corresponding sesamoid bone, a few fibres passing on to re-unite below 

 the joint and become continuous with the tendon of the extensor pedis in 

 front of the os coronse. 



The synovial capsule of the fetlock joint is prolonged forwards in the form 

 of a cul cle sac lining the bifurcation of the suspensory ligament. There is also 

 frequently developed, in front of the joint, a pouch communicating with 

 this capsule which lines the posterior surface of the extensor tendons. 



The movements of the fetlock joint are almost entirely confined to flexion 

 and extension, a very slight lateral motion being permitted when the liga- 

 ments are relaxed, as in passive flexion of the leg. 



