a THE ANKLE-JOINT. 297 
—— 
into three fasciculi, which are distinguished from each other by names descriptive 
of their chief points of attachment. 
The anterior fasciculus (lig. talo-fibulare anterius) is the shortest. It extends 
from the anterior border of the external malleolus to the astragalus immediately in 
front of its external articular surface. 
The middle fasciculus (lig. calcaneo-fibulare) is a strong and rounded cord. It 
is attached by one end to the front of the tip of the external malleolus, and by 
the other to the outer side of the os calcis, immediately above the groove for the 
peroneal tendons. . 
The posterior fasciculus (lig. talo-fibulare posterius) is the strongest. It runs 
transversely between the lower part of the fibular fossa on the inner aspect of the 
malleolus and the posterior surface of the astragalus, where it is attached to the 
external tubercle and the adjoining rough surface. Sometimes this tubercle is 
detached from the astragalus, and represents a separate bone—the os trigonum. 
The internal lateral ligament (lig. deltoideum, Figs. 227 and 228) has the general 
shape of a delta, and is even stronger than the external hgament. It is attached above 
\ Dorsal astragalo-scaphoid ligament 
i , 4 . . 
Dorsal and internal scapho-cuneiform ligaments 
Dorsal intercuneiform ligaments 
Dorsal and internal lateral tarso-metatarsal ligaments 
Wis 
Internal lateral ( ——[—“77Aii 
a ye Sana} ay Mi . 
ligament of ankle | ij Dorsal and internal lateral meta- 
tarso-phalangeal ligaments 
Dorsal and internal 
lateral interphalan- 
geal ligaments 
Tibio-astragaloid 
ligament 
Inferior caleaneo- 
scaphoid ligament 
Fic. 228.—LIGAMENTS ON INNER ASPECT OF ANKLE AND FOOT. 
to a marked impression on the lower part of the internal malleolus, and below, in a 
continuous layer, to the scaphoid, astragalus, and os calcis. In it we may recog- 
nise the following special bands—(a) the lig. talo-tibiale anterius, which extends 
from the front of the inner malleolus to the neck of the astragalus; (6) the lig. 
talo-tibiale posterius, stretching between the back of the inner malleolus and the 
postero-internal rough surface of the astragalus; (¢) the lig. tibio-naviewlare, which 
extends from the tip of the inner malleolus to the inner side of the scaphoid; (d) 
the lig. calcaneo-tibiale, which extends between the tip of the inner malleolus and 
the inner side of the sustentaculum tali; (e) the lig. talo-tibiale profundum, which 
consists of deeper fibres extending from the tip of the internal malleolus to the 
inner side of the astragalus. 
Synovial membrane lines the capsular ligament, and, as already described, the 
joint-cavity communicates directly with the inferior tibio-fibular joint. Both at 
the front and back of the ankle-joint, as well as superiorly in the angle formed by 
the three bones, the synovial membrane covers pads of fat. 
Movements at the Ankle-Joint.—In the erect attitude the foot is placed at right angles to 
the leg; in other words, the normal position of the ankle-joint is flexion. Those movements 
which tend to diminish the angle so formed by the dorsum of the foot and the front of the 
leg, are called dorsiflexion, while those which tend to increase the angle, 7.e. to straighten the 
foot upon the leg, are called extension. As a matter of fact neither dorsiflexion nor extension 
are ever completely carried out, and the range of movement of which the foot is capable is limited 
to about 90°. These movements oceur about an obliquely transverse axis, as is indicated by the 
natural outward pointing of the toes. The weight of the body falls slightly anterior to the ankle- 
joint, so that a certain amount of muscular action is necessitated in order to maintain the foot 
at right angles to the leg; but additional stability is obtained from the obliquity above 
mentioned. 
When the foot is raised from the ground, muscular action tends naturally to produce a certain 
amount of extension. When the foot is extended, as in standing on the toes, the hinder narrow 
part of the astragalus moves forwards into the wider part of the interval between the tibia and 
