The Ankle and Foot 331tion of the talus lies within the malleoli, allowing for
more joint play and less stability (figure 6.34C). This
position of plantar flexion relies more on ligaments
and muscles for stability and is commonly involved
in the mechanism of ankle sprains.
Influence of Pronation
and Supination on Foot Mechanics
In movement, transfer of the body weight and rela-
tive positioning of the bones of the feet can function
to make the foot more or less stable (Levangie and
Norkin, 2001). The position of supination places the
weight of the body on the lateral longitudinal arch,
which is designed for stability; and due to ligament
design and axes of the transverse tarsal joint the foot
is “locked” and stable. This stable position of the foot
is desirable for transfer of weight to the foot and for
providing a stable segment about which the rest of
the body may move, as well as for use of the foot as
a rigid lever for propulsion in movements such as
walking, running, or jumping. However, the foot also
has the need to be able to accommodate to uneven
surfaces and absorb shock. These qualities are met by
pronation, in which the foot “unlocks” and becomes
the flexible structure necessary to allow for small
movements between the tarsals and movement of
the forefoot relative to the rearfoot. This pronation
also shifts the weight of the body toward the medial
longitudinal arch of the foot, which is designed
for mobility. Thus, the arrangement of the various
arches and joints allows the foot to act as a rigid lever
for propulsion and an adaptive structure for force
absorption and accommodation, initiated by use of
the positions of supination and pronation.
Muscular Analysis of Fundamental Movements of the Ankle and Foot
Movements are simplified in this discussion to ankle-
foot dorsiflexion, ankle-foot plantar flexion, foot
inversion, and foot eversion without differentiation
regarding the contribution of the various joints of the
rearfoot and midfoot. Also for purposes of simplifica-
tion, movements of the toes are not discussed in the
text but merely included in table 6.4. When thinking
about the movements of the toes, it is important to
keep in mind that one of the key functions of the
toes is to press down against the ground to propel
the body in space. A summary of the key muscles
capable of producing the fundamental movements
of the ankle and foot is provided in table 6.4.
Plantar Flexion
Ankle-foot plantar flexion involves bringing the ante-
rior surface of the shin and the dorsum of the foot
away from each other. For example, the triceps surae
and other plantar flexors of the foot (table 6.4) are
used concentrically to point the foot as in tendus,
dégagés, or the sitting point (table 6.6B, p. 344) when
the foot is not weight bearing. When the foot is weight
bearing, the same muscles are used to rise onto the
toes, such as in pointe work (figure 6.35) and the calf
raise (table 6.6A, p. 343) or to propel the body into
space, as in jumps (table 6.6C, p. 345). Although many
muscles are capable of producing plantar flexion,
due to their size and location (effective leverage due
to large distance of Achilles tendon from the axis of
the ankle joint), the gastrocnemius and soleus are
the primary muscles, while other muscles can make
only a small contribution. Their primary importance
is demonstrated by the inability of an individual to
rise onto the toes when paralysis of the triceps surae
is present (Smith, Weiss, and Lehmkuhl, 1996).FIGURE 6.35 Sample dance movement showing ankle-
foot plantar flexion.
Photo by Richard Newman. Dancer: Lauren Newman with Inland Ballet Theatre.