The Ankle and Foot 303primarily in a transverse plane around a vertical axis,
more akin to horizontal abduction-horizontal adduc-
tion of the shoulder or hip. The slight dorsiflexion
and plantar flexion that occurs is in the same direc-
tion as described with the ankle but involves the talus
upon the calcaneus rather than the talus relative to
the mortise joint.
Ankle Joint Capsule
and Rearfoot Ligaments
The ankle joint is surrounded by a thin fibrous cap-
sule that is relatively weak, but it is reinforced on each
side by strong ligaments, called the medial and lateral
collateral ligaments. Other closely approximated
ligaments hold the tibia and fibula together at the
mortise joint (anterior and posterior tibiofibular
ligaments), and still others provide key stability to
the subtalar joint.
Medial Collateral Ligament
The medial collateral ligament (collateral, side by
side)—also called the deltoid ligament (G. deltoeides,
triangular)—is composed of four parts that fan out
from their attachment on the medial malleolus to
their respective attachments on the surrounding
bones. As can be seen in figure 6.5, one division
runs downward (tibiocalcaneal ligament) from the
medial malleolus to attach onto the medial aspect
of the calcaneus; two components run from the
medial malleolus diagonally downward and forward
to attach onto the talus and navicular (anterior tib-
iotalar ligament and tibionavicular ligament); and
the last component runs from the medial malleolus
diagonally downward and backward to attach onto
the talus (posterior tibiotalar). Together these liga-
ments prevent forward or backward displacement of
the tibia or of the talus and are vital for providing
medial stability to the ankle joint. Because one band
attaches onto the calcaneus, the deltoid ligament also
provides stability for the subtalar joint and helps limit
eversion and abduction of the foot. These ligaments
also help link movements between the tibia, ankle
joint, and subtalar joints, particularly inversion of the
foot and external rotation of the tibia (Hintermann,
1999). As with the knee, the integrity and function of
the ligaments can be demonstrated by manual stress
tests performed by a physician. If the medial side of
the joint opens up and a gap is formed with eversion,
injury to the deltoid ligament is suggested.
The deltoid ligament is very strong and extensive.
This strength is important because the medial mal-
leolus does not extend distally as far as the lateral,
and so the lesser stability from bony architecture is in
part compensated for by the greater massiveness of
the medial ligaments. In fact the deltoid is so strong
that when forces are large enough to cause injury, the
medial malleolus may be avulsed and other bones
fractured rather than the deltoid ligament’s being
ruptured.Lateral Collateral LigamentThe lateral collateral ligament is composed of three
discrete bands, shown in figure 6.6, that connect the
lateral malleolus with adjacent bones of the foot. The
anterior talofibular ligament (ATFL) runs almostFIGURE 6.5 Key ligaments of the medial aspect of the
ankle (right foot).
FIGURE 6.6 Key ligaments of the lateral aspect of the
ankle (right foot).