Dance Anatomy & Kinesiology

302 Dance Anatomy and Kinesiology

axis for this movement is close to a frontal plane, but

it deviates slightly posteriorly and inferiorly from the

medial to lateral side, and it also does not stay fixed

but rather shifts slightly with dorsiflexion and plantar

flexion. You can obtain a rough estimate of the axis

by putting your thumb and forefinger on the medial

and lateral malleolus and imagining a line running

through these points. However, there are very large

individual differences, and divergent averages are

given by different sources for the location of this

axis. For example, Levangie and Norkin (2001) hold

that on average the axis is rotated laterally 20° to 30°

in the transverse plane and inclined 10° downward

on the lateral side, while Kreighbaum and Barthels

(1996) suggest much lower average values of 13°

rotation and 7° inclination.

Subtalar Joint

Classification and Movements

The subtalar joint (L. sub, under + talar, relating

to talus) is formed between the inferior portion of

the talus and the superior portion of the calcaneus

(figure 6.3). The articular surfaces of these bones

fit well together, and additional stability is provided

by a flattened area on the medial calcaneus termed

the sustentaculum tali (L. sustenataculum, a prop or

support + tali, relating to talus) that acts like a shelf

to help support the medial talus. This joint is gener-

ally classified as a gliding synovial joint (Moore and

Dalley, 1999), but it allows more movement than is

often associated with a gliding joint.

The specialized terminology of inversion-eversion,

abduction-adduction, and plantar flexion-dorsiflexion can

be used to describe these movements (figure 6.4).

Inversion involves lifting the inner border of the

foot so that the distal portion of the calcaneus and

sole of the foot face medially or inward. Eversion is

the opposite movement, involving lifting the outer

border of the foot so that the distal heel and sole of

the foot face laterally. Abduction can be thought of

as moving the forefoot away from the median plane

or midline of the body, while adduction refers to

the opposite movement of the forefoot toward the

midline of the body. Note, however, that this special-

ized form of abduction-adduction of the foot occurs

FIGURE 6.4 Movements of the ankle and foot.

(Metatarsophalangeal

joint)

(Metatarsophalangeal

joint)

(Metatarsophalangeal

joint)