_21_, Tibia; _24_, tuber calcis. (After Ellenberger-Baum, Anat. für
Künstler.)
]
The =internal lateral ligament= (Ligamentum collaterale tibiale longum
et breve) also consists of two parts which cross each other. The =long
ligament= arises on the posterior part of the internal malleolus,
becomes wider below, and is attached on the lower tuberosity of the
tibial tarsal, the large and outer small metatarsal bones, and the inner
surface of the lower tarsal bones which it covers. The =short ligament=
lies largely under cover of the long one. It extends from the anterior
part of the internal malleolus, runs backward and somewhat downward, and
divides into two branches; one of these ends on the upper tuberosity on
the inner surface of the tibial tarsal bone, the other on the
sustentaculum tali.
The =plantar= or =calcaneo-metatarsal ligament= (Ligamentum tarsi
plantare) is a very strong flat band which covers the outer part of the
posterior surface of the tarsus. It is attached to the posterior surface
of the fibular and fourth tarsal bones and the proximal end of the
external metatarsal bone.
The =dorsal= or =oblique ligament= (Ligamentum tarsi dorsale) is a
triangular sheet which is attached above to the lower tuberosity on the
inner face of the tibial tarsal bone, and spreads out below on the
central and third tarsal bones, and the proximal ends of the large and
inner small metatarsal bones, to all of which it is attached.
=Special Ligaments.=—A considerable number of short bands which connect
adjacent bones of the tarsus and metatarsus are described by various
authors; some of these are quite distinct; others are difficult to
isolate. Most of them are not of sufficient importance to justify
detailed description.
(1) The =tibial= and =fibular tarsal= bones are united by four bands
(astragalo-calcaneal ligaments). The =internal ligament= extends from
the sustentaculum tali to the adjacent part of the tibia tarsal,
blending with the short lateral ligament. The =external ligament=
extends from the anterior process of the fibular tarsal to the
adjacent part of the external ridge of the trochlea. The =superior
ligament= extends from the posterior margin of the trochlea to the
fibular tarsal. The =interosseous ligament= is deeply placed in the
sinus tarsi between the two bones, and is attached in the rough areas
of the opposed surfaces.
(2) The smaller bones are attached to each other as follows: The
central and third tarsal are united by an interosseous and an oblique
anterior ligament (scaphoido-cunean ligaments). The central and fourth
tarsal are united by an interosseous and a transverse external
ligament (cuboido-scaphoid ligament). The third and fourth tarsals are
similarly connected (cuboido-cunean ligaments). The third tarsal is
joined by an interosseous (intercunean) ligament to the (fused) first
and second tarsals; the latter are connected with the fourth tarsal by
a transverse posterior ligament.
(3) The smaller bones are connected with the upper row as follows: The
central is attached to the tibial tarsal by posterior and interosseous
(astragalo-seaphoid) ligaments, and to the fibular tarsal by a short
oblique (calcaneo-scaphoid) band. The fourth is attached to the
fibular tarsal by interosseous and posterior (calcaneo-cuboid)
ligaments. The (fused) first and second tarsals are connected with the
fibular tarsal by a posterior (calcaneo-cunean) ligament.
(4) The lower tarsal bones are connected with the metatarsus by
tarso-metatarsal ligaments, which are not distinct from the common
ligaments, except in the case of the interosseous ligament between the
third tarsal and metatarsal bones.
[Illustration:
FIG. 166.—SAGITTAL SECTION OF HOCK OF HORSE.
]
=Movements.=—These are flexion and extension, which take place at the
tibio-tarsal joint. The movements between the tarsal bones, and between
the latter and the metatarsus, are so limited as to be negligible so far
as the action of the joint as a whole is concerned. In the standing
position the articular angle (in front) is about 150° to 160°. Complete
extension is prevented by tension of the lateral ligaments. Flexion is
checked only by contact of the metatarsus with the leg, provided the
stifle joint is also flexed. Owing to the fact that the axis of motion
is slightly oblique, the lower part of the limb deviates somewhat
outward during flexion.
The movements of the hock joint must correspond with those of the
stifle on account of the tendinous bands in front and behind (peroneus
tertius and flexor perforatus), which extend from the lower part of
the femur to the tarsus and metatarsus.
The remaining joints differ in no material respect from those of the
thoracic limb.