The Ankle and Foot 299contact with the upper surface of the large tarsal
bone called the talus (L. ankle, ankle bone, figure
6.2A) to form the ankle joint.
The talus is often termed the cornerstone of the
foot because forces coming down from the lower leg
are translated forward and back on the foot through
the talus. The talus sits on the largest tarsal bone,
the calcaneus (L. calcaneum, heel). The calcaneus
projects backward to form the “heel” and can be
easily palpated in the heel area. There is a small space
formed between a portion of the talus (its narrower
neck) and the underlying calcaneus that is termed
the tarsal tunnel or canal. This bony tunnel opens
up laterally as a small bony depression filled with
soft tissues called the sinus tarsi (L. sinus, cavity + G.
tarsus, sole of the foot) (figure 6.2B). This landmark
is important for locating the lateral ligaments of
the ankle and is often a site of swelling with lateral
ankle sprains.
Anteriorly, the calcaneus articulates with the
tarsal bone called the cuboid (G. kybos, cube + eidos,
resemblance) as seen in figure 6.2B, and the talus
articulates with the tarsal bone called the navicular
(L. boat shaped) as seen in figure 6.2A. The navicular
contains a small projection termed the tubercle of
the navicular (L. tuberculum, a swelling). This projec-
tion can be palpated about 1 to 1 1/2 inches (2.5-3.8
centimeters) anterior to and about a finger breadth
below the medial malleolus. This landmark can be
used for evaluation of the arches of the feet.
The remaining three tarsal bones, termed the
cuneiforms (L. cuneus, wedge), are located in a rowFIGURE 6.2 Bony landmarks of the foot (left foot). (A) Medial view, (B) lateral view.