Its location and mode of articulation with the tibia and the fibula.
The human talus (G in figs. 1, 2, all of figs. 3-6; W to F and Y
in the skeletons, and next to a and b)
corresponds in shape to the talus of dogs, bears, and similar animals whose
feet are divided into digits, but not of animals with a cloven or solid hoof)
is contained beneath the tibia and fibula, a large portion of its surface
enclosed by the epiphyses of those bones, as I have previously related in my
descriptions of the tibia and fibula.
The upper part of the talus, which faces upward
whenever the entire foot presses upon the ground, projects with a conspicuous
and quite smooth tuberosity
[trochlea tali, facies superior] (A-D in figs 3, 5,
6) coated with slippery cartilage
[cartilago articularis] and not
unlike the quarter part of a small wheel.
This projection of the talus is round
and smooth like that part of a wheel, and ends in four sides or flanks. The
[medial] (A to B in figs. 3, 5, 6)
and the second
[lateral] (C to D in figs. 3, 5, 6)
are brought as if in a circle at the sides of the projection along its
longitude; the third
[distal] (A to C in the same
figures) runs along the anterior edge of the projection, the fourth
[proximal] (B to D in the same
figures) along the posterior edge. In such a way, this orbicular projection of
the talus is somewhat quadrangular, and for this reason it is called te/trwron
by the Greeks and quatrio by the Latins.
projection resembles the fourth part of a small wheel not just in its sides,
but like a pulley on which a rope is turned it has a rather lightly carved
depression (E, E in fig. 3) in its middle, and protrudes more towards either
[trochlea tali, facies superior] (F, F in fig. 3),
precisely matching the surface
[facies articularis, inferior
tibiae] (d, e, f in fig. 9,
10, ch. 31) which we have written is provided in the lowest surface of the
epiphysis of the tibia to receive the talus. By means of this connection of the
talus to the tibia we flex and extend the foot, and move it to the sides enough
to be visible — though we would accomplish a more complete movement to the
sides if the projection or quatrio
of the talus were carved less like a pulley and less
closely articulated to the tibia;
Depressions of the talus by which it receives ligaments from the tibia and fibula
Just as we have written that the inner 49 side of the inner malleolus makes a rough depression [sulcus malleolaris] (k in figs. 4, 10, ch. 31) from which originates a cartilaginous ligament 50 (f in the figure for ch. 1, Bk. 2) attaching the talus to the tibia, so also the inner side of the talus is hollowed by a rough depression (I in fig. 5) to receive this ligament; the outer side of the talus is similarly carved out (K in fig. 6) so that the ligament 51 (g in the figure for ch. 1, Bk. 2) brought from the inner side of the outer malleolus may be inserted into it. Because of such ligaments, the posterior surface of the talus [proc. posterior tali] situated near the root (behind B and D in fig. 5) of the projection or trochlea is rough to admit ligaments originating from the tibia and to extend others to the calcaneus.
Depressions by which it brings down tendons
But besides roughness of this sort, the posterior area of the talus also shows depressions (L, M in figs. 5 and 6, or 1, 2, 3 in the 15th table of muscles) provided to convey the tendons of muscles which enter the bottom of the foot by this route. The tendon of the fifth of the muscles [m. tibialis posterior] that move the foot, of the muscle [m. flexor hallucis longus] that flexes the second bone of the big toe, and of the muscle [m. flexor digitorum longus] that flexes the third bone in each of the four other toes (D, E, O, P mark the muscles in the same table of muscles), descend by this route. That is the way the talus is articulated to the tibia, and how the upper and posterior areas and the sides of the talus are arranged. 52
Joint of the talus with the bone resembling a boat
From its anterior part and more from the inner side of this area, a long neck [collum tali] (N in figs. 3-6) is extended which proceeds some distance and ends in a round head [caput tali] (O in the same figs.) coated with slippery cartilage. This is articulated into the deep depression [facies articularis navicularis] (k in fig. 11) of the navicular bone, forming the joint by which we believe the foot is moved slightly and in an obscure motion to the sides, and swiveled.
Attachment of the talus to the calcaneus
The lower part of the talus is articulated to the bone of the heel by two joints, and is entirely laid upon it. One joint is situated in the posterior region, where the heelbone projects in a wide, ample tuberosity [calcaneus, facies articularis talaris posterior] (P in figs. 7, 8, 9) entering the wide, deep depression [facies articularis calcanea posterior] (Q in fig. 4) of the talus. The other joint is anterior [calcaneus, facies articulares talaris anterior et media], verging toward the inner side of the foot; it is arranged differently from the posterior joint. The calcaneus is carved with an oblong depression [calcaneus, facies articularis talaris media] (R in figs 7, 8, 9) which is coated with cartilage and receives the lower part [facies articularis calcanea media] (S in fig. 4) of the head of the talus. The head of the talus (O in fig. 4), articulated with the navicular bone, is precisely fitted on its lower surface [facies articularis calcanea anterior] to the depression of the calcaneus [facies articularis talaris anterior] just mentioned where it rests upon the heelbone with a low projection. 53
Depression appearing between the attachments of the talus with the calcaneus
Between these articulations, the talus (T, T in fig. 4) [sulcus tali] and the calcaneus (V, V in figs. 7, 8, 9) [sulcus calcanei] are both made rough and have deep depressions from which originate cartilaginous ligaments [lig. talocalcaneum interosseum] very powerfully binding the talus to the calcaneus. The rough depressions in these bones are so deeply incised that when the bones are cleaned and afterwards reassembled a large space [sinus tarsi] lies open there between the talus and the calcaneus, which is filled in the living with cartilaginous ligaments [lig. talocalcaneum laterale, lig. talocalcaneum mediale] of the sort which bind the talus to the calcaneus so tenaciously that it can scarcely be moved at all and is as immovable on its lower surface [articulatio subtalaris] as it can be seen to twist and turn freely on its upper surface where it is articulated [articulatio talocruralis] with the tibia.