Fig. 60.--The patella has been removed. 1, femur; 2, tibia; 3,
fibula. _a_, patellar surface of femur; _b_, tubercle for attachment
of ligamentum patellæ; _c_, medial meniscus; _d_, lateral meniscus;
_e_, _f_, ligaments of the menisci; _g_, ligamentum cruciatum
anterius; _h_, ligamentum cruciatum posterius; _i_, ligamentum
collaterale tibiale; _j_, ligamentum collaterale fibulare.
Fig. 61.--The capsule of the joint has been opened. 1, femur; 2, tibia
(fibula not shown); 3, sesamoid bone in lateral head of M.
gastrocnemius; 4, sesamoid in medial head of M. gastrocnemius; 5,
tendon of M. popliteus, with sesamoid bone; 6, 7, lateral and medial
condyles of the femur, with the intercondyloid notch between them; 8,
9, lateral and medial condyles of the tibia, with the popliteal notch
between them; _a_, _b_, medial and lateral menisci; _c_, ligamentum
cruciatum anterius; _d_, ligamentum cruciatum posterius; _e_, _f_,
ligaments of the lateral meniscus; _g_, ligamentum collaterale
tibiale.]
(3) CRUCIAL LIGAMENTS.--There are two of these also. The =ligamentum
cruciatum anterius=, or anterior crucial ligament (Fig. 60, _g_; Fig.
61, _c_), is a thick, strong ligament which begins on the dorsal part of
the proximal end of the tibia nearer the medial side (Fig. 60, _g_), and
passes ventrad and proximad, between the ends of the two bones forming
the joint, into the intercondyloid fossa of the femur, and becomes
attached to the medial surface of the lateral condyle of the femur (Fig.
61, _c_). It is composed of two partially separated bands, forming a
slight angle with one another. It is crossed near its dorsal and ventral
ends by two of the ligaments of the menisci. The =ligamentum cruciatum
posterius=, or posterior crucial ligament (Fig. 60, _h_; Fig. 61, _d_),
begins on the tibia at the edge of the popliteal notch (Fig. 61, _d_),
nearer the medial side, and passes dorsad and proximad to be attached to
the ventral edge of the patellar surface of the femur, in the
intercondyloid fossa (Fig. 60, _h_).
(4) LIGAMENTS OF THE MENISCI.--There are five of these, connecting the
menisci with the femur or tibia. One (Fig. 60, _e_) passes from the
dorsal edge of the medial meniscus (_c_) transversely across the
anterior crucial ligament (_g_) to the proximal end of the tibia nearer
the lateral side. A second (Fig. 60, _f_) passes from the dorsal margin
of the lateral meniscus (_d_) transversely beneath the anterior crucial
ligament (_g_) to the proximal end of the tibia nearer the ventral side
and medial border. A third (Fig. 61, _f_) passes from the ventral margin
of the lateral meniscus obliquely across the anterior crucial ligament
(_c_) to the lateral side of the medial condyle of the femur. The fourth
(Fig. 61, _e_) is small, passing from the medial angle of the ventral
border of the lateral meniscus distad to the popliteal notch. The fifth
passes from the ventral border of the medial meniscus laterad beneath
the posterior crucial ligament to the proximal end of the tibia, nearer
the ventral and lateral sides.
=Articulations between the Tibia and Fibula.=--At the proximal end the
fibula is as it were suspended from the distal side of the overhanging
lateral tuberosity of the tibia by strong ligamentous tissue. The
capsule of the joint is formed by an extension of the capsule of the
knee-joint which passes between the tibia and fibula on the ventral
side. Forming the dorsolateral wall of this extension is a strong, thick
ligament which passes directly from the head of the fibula to the
lateral surface of the lateral tuberosity of the tibia. A second more
delicate ligament passes from the head of the fibula dorsoproximad to
the tubercle laterad of the crest of the tibia, bridging a groove
through which passes the tendon of M. extensor longus digitorum.
The tibia and fibula are connected throughout their length by an
=interosseus membrane=. This is broad and very thin in its proximal
part, narrower and thicker distad.
Distad the two malleoli forming the ends of the fibula and tibia are
closely and immovably united. The capsule of the joint is here an
extension proximad of the capsule of the articulation with the
astragalus. On the dorsal side a short broad band of strong fibres
passes from the surface of the tibia obliquely laterodistad to the
border of the fibula; this forms the =anterior ligament= of the =lateral
malleolus=. On the ventral side a very much weaker set of fibres forms
the ventral wall of the articular capsule; it is called the =posterior
ligament= of the =lateral malleolus=. Tibia and fibula are also
connected on the dorsal side by the =ligamentum transversum cruris=, or
transverse ligament of the lower leg (Fig. 91, 5), which spans the
tendons of Mm. extensor longus digitorum and tibialis anterior. From the
middle of the distal margin of this a slender supporting ligament passes
distad and is inserted on the dorsal surface of the tarsus. The grooves
in the two malleoli for the passage of the tendons are spanned by
ligamentous fibres (retinacula) for holding the tendons in place.
=Articulation between the Leg and the Foot.=--At the distal end there is
formed between the two malleoli a deep irregular fossa, into which is
received the trochlea of the astragalus. The joint is covered by a
large =articular capsule=, which passes also, as above noted, between
the tibia and fibula. In addition to the capsule the following ligaments
may be distinguished: (_a_) On the lateral side, (1) a short ligament
from the fibula to the astragalus, directed toward the proximal end of
the foot; (2) a ligament from the fibula to the calcaneus, attached to
the latter proximad of the peroneal tubercle; (3) a stronger ligament
from the fibula to the calcaneus, lying beneath the last-mentioned and
directed toward the proximal end of the bone. (_b_) On the medial side
may be distinguished (1) a strong ligament from the tibia (medial
malleolus) to the sustentaculum tali, and passing thence onto the
scaphoid; (2) a short ligament from the medial malleolus to the
astragalus.
=The Tarsus.=--The articulations between the separate bones of the
tarsus and between the tarsus and metatarsus have a considerable number
of variously communicating articular capsules. The separate bones are
connected by many ligaments. The ligaments of the ventral surface
(=ligamenta plantaria=) are especially well developed. Here may be
noticed particularly a very large =calcaneocuboid= ligament, and a large
=calcaneocuneiform= ligament which passes from the sustentaculum tali to
the medial cuneiform. Those on the dorsal surface (=ligamenta dorsalia=)
are less strong and numerous. Many ligaments, longitudinal, transverse,
and oblique, pass also between the separate bones (=ligamenta
interossea=). =Ligamenta lateralia=, on the lateral and medial borders
of the foot, are also distinguishable. Strauss-Durckheim enumerates
ninety-four ligaments of the tarsus; an account of each of these does
not form part of the plan of the present work.
The ligaments of the metatarsus and phalanges are of the same general
character as in the forelimb. Of these Strauss-Durckheim enumerates
thirty-six; they will not be described here.