PASTERN JOINT. 373 
2. The ligaments connecting the cannon-bone to the pastern (or, in scien- 
tific language, the metacarpus to the 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 suffraginis, where it is fixed, by mixing its 
fibres with the lateral sesamoideal hgaments. 
The capsular 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. 
The suspensory ligament, which should be carefully studied on account 
of the numerous accidents to which it is liable, is attached to all four of 
the 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 corone. 
The synovial capsule of the fetlock joint is prolonged forwards in the 
form of a cul de sac lining the bifurcation of the suspensory ligament. 
There is also frequently developed, in front of the joint, a pouch com- 
municating 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 ligaments are relaxed, as in passive flexion of the leg. 
THE PASTERN JOINT. 
The several parts which enter into the formation of this joint are the 
two lateral condyles on the inferior extremity of the os suffraginis, and 
the corresponding cavities on the os coronz. This last surface is com- 
pleted behind by a very dense and thick fibro-cartilage, which acts partly 
as a ligament, and partly by increasing the depth of the articular surface. It 
is attached above by six fibrous bands, of which two are continuous with 
the inferior sesamoideal ligaments, and four pass on to the sides of the os 
suffraginis. Below it is fixed to the os coron, between the articular sur- 
face and the tubercle behind it. This fibro-cartilage forms a smooth surface 
posteriorly for the flexor pedis perforans to play over, and is continuous 
