Week 11: ankle/foot

Question 1

Distal tibia

Answer 1

 In adults the distal portion of the tibia is externally rotated
in the transverse plane with respect to the proximal end
of the tibia (approx. 20-30°), creating a normal or lateral
tibial torsion

Question 2

Tibiofibular joints

Answer 2

 The proximal tibiofibular joint (gliding joint)
& the distal tibiofibular joint (syndesmosis)
are supported by ligaments and an
interosseous membrane
 These joints work together to
accommodate the rotation of the tibia
during knee motion and the multiplanar
motion of the foot
 The distal tibiofibular joint also provides
essential stability to the talocrural joint
- The foot must function to (1) support body weight, (2) adapt to uneven surfaces,
(3) attenuate ground contact forces, and (4) act as a rigid lever during propulsion

Question 3

Movement

Answer 3

 Dorsi-plantar flexion occurs in the sagittal plane around
a medial-lateral axis
 Occurs primarily at the talocrural joint
 Abduction-adduction occurs in the transverse plane
around a vertical (longitudinal) axis that is described as
parallel to the long axis of the tibia
 Inversion-eversion occurs in the frontal plane about an
anterior-posterior axis (the long axis of the foot), which
lies within the second metatarsal of the foot
 Occurs primarily at the subtalar and transverse tarsal joints

Question 4

Pronation-Supination

Answer 4

 Pronation and Supination describe motion
around a single axis that has components of
motion in three planes
 These motions always occur together
- Sagittal plane component - pronation (dorsiflexion) supination (plantarflexion)
- Frontal plane component pronation (eversion) supination (inversion)
- Transverse plane component pronation (abduction) supination (adduction)

Question 5

Distal tibiofibular & talocrural joints

Answer 5

 Articulation between the
tibia & fibula with the talus
 The concave shape of the
distal aspect of the tibia
and fibula is maintained
by strong connective
tissue

Question 6

Talocrural (ankle) joint

Answer 6

 Articulating surfaces increase
the contact area which
reduces the stress
 Joint stability increases with
loading and this is important
because 90-95% of
compressive loads pass
through the tibia & talus
 Articular cartilage (blue) is thinner but stiffer than that in the
knee/hip and this stiffness may protect against degeneration
- Axis of rotation passes through
the body of the talus and
through the tips of both malleoli
- In most clinical situations the obliquity of the joint axis is considered so minor that
the components of the other two planes are ignored and the ankle is suggested to
function in the sagittal plane alone as a hinge joint consisting of DF and PF

Question 7

Subtalar joint

Answer 7

 Articulation between the talus and the calcaneus
 It is critical during walking because:
- It acts to translate the motion of the tibia to the foot or
the rotation of the foot to the tibia
- It’s mobility allows the foot to assume positions that
are independent of the orientation of the ankle and leg
above. This is important for walking on sloped
surfaces or when quickly changing direction

Question 8

Subtalar joint continued

Answer 8

 This mobility is achieved by
the fact that there are number
of facets with different
configurations that allow a
range of movements
 The collateral ligaments
contribute to stability at the
subtalar joint, preventing
excessive motion
- Obliquity of the axes allow equal
amounts of the component motions:
(1) inversion/eversion
(2) abduction/adduction
DF/PF is negligible
- In non-weight bearing the talus is stationary and the calcaneus moves on the
talus. In weight bearing the calcaneus is stationary and the talus moves on the
calcaneus

Question 9

Summary for talocrural joint and subtalar joint

Answer 9

 The primary motion at the talocrural joint is dorsi-plantar
flexion while the primary motions at the subtalar joint are
inversion-eversion and abduction-adduction so the
combination of these two joints provide motion in all
three planes
 The talocrural joint provides primarily for forwards
progression during walking while the subtalar joint
provides freedom for the lower leg to rotate in the
transverse or frontal planes without requiring the foot to
move on the ground

Question 10

Ankle complex ligaments

Answer 10

 A joint capsule and collateral
ligaments provide important
passive stability to the ankle
 The medial (deltoid) complex
resists eversion while the lateral
complex resists inversion
 Both complexes also limit
anterior-posterior translation of
the talus within the mortise

Question 11

Other joints

Answer 11

 Transverse tarsal (midtarsal) joint
- important relationship with the subtalar joint in gait
 Distal intertarsal joints
 Tarsometatarsal joints (gliding joints)
 Metatarsophalangeal joints (biaxial condyloid – flexionextension
& abduction-adduction)
 Interphalangeal joints (uniaxial hinge – flexion-extension)

Question 12

Forefoot

Answer 12

 The function of the forefoot is to maintain the:
- Medial longitudinal arch
- Transverse metatarsal arch
- Mobility of the first metatarsal
 Mobility at the first metatarsal (as part of the first
ray) is important because it has considerable
involvement in weight bearing and propulsion
during gait

Question 13

Arches

Answer 13

 The three arches of the foot
serve several purposes:
- Protect the nerves blood vessels
and muscles on the plantar
surface of the foot from
compression during weight bearing
- They help to attenuate load during
ground contact
- They help store mechanical
energy then release it to improve
the efficiency of walking
 Supported by fascia, ligaments,
and muscle

Question 14

Medial longitudinal arch

Answer 14

 The medial longitudinal arch is
the primary load bearing and load
attenuating structure of the foot
 Primary passive support is
provided by the plantar
aponeurosis (also spring ligament)
 As loads increase during
movement muscle contraction
(e.g. tibialis posterior) may also
provide dynamic support

Question 15

Medial longitudinal arch

Answer 15

 Active toe extension (particularly
when combined with plantar flexion)
pulls the plantar aponeurosis taut
and stabilises the foot
= windlass mechanism
 This is useful in activities such as
standing on the toes or during the
propulsive phase of gait
 In this position tibialis posterior and
peroneus longus form a functional
sling that supports the arch

Question 16

Medial longitudinal arch

Answer 16

 Individuals can be classified
according to the height of the
medial arch into 3 foot types:
- Normal (typical)
- High arched (pes cavus)
- Flat-footed (pes planus)
 They can be further
classified as being
rigid or flexible

Question 17

Anterior compartment

Answer 17

 Two important functions for
the DFs during gait:
- Provide adequate ground
clearance during the swing phase
- Eccentrically control PF as the
foot is lowered to the ground after
contact
 Stabilised by the extensor
retinaculum

Question 18

Lateral compartment

Answer 18

 Fibularis (peroneus) longus &
brevis are the primary evertors
and provide the main source of
dynamic stability to the lateral
ankle
 The tendons of these muscles
run posterior to the lateral
malleolus so they act as plantarflexors

Question 19

Posterior compartment - superficial

Answer 19

 Soleus -
- Has the largest PCSA of all muscles of the lower leg
- Has a relatively high proportion of type 1 fibres so is well
suited for postural control
- The ‘work-horse’ of plantar-flexion
 Gastrocnemius -
- Is critical in activities requiring high
force production
- Is most effective as a plantar-flexor
when the knee is extended and the
ankle is dorsi-flexed (sprint start)

Question 20

Posterior compartment - deep

Answer 20

 Tibialis posterior is an important
stabiliser of the forefoot
 This muscle may also assist with the
gradual and controlled lowering of
the medial longitudinal arch during
weight bearing

Question 21

Summary - Interaction during gait

Answer 21

 After ground contact in walking
gait two opposing vertical forces
acting on either side of the axis
of rotation in the subtalar joint
create eversion of the rearfoot
 This pronation of the ankle-foot
complex “unlocks” the transverse
tarsal joint and makes the foot
more mobile so that it can adapt
to the walking surface

Question 22

Interaction during gait

Answer 22

 Pronation of the ankle-foot complex is also
accompanied by internal rotation of the tibia and
flexion of the knee, thereby enhancing the mobility
and load attenuating capacity of the lower extremity
as a whole
 The medial longitudinal arch lowers slowly in
response to the progressive increase in body
weight over the support limb. The plantar
aponeurosis and if needed tibialis posterior control
this lowering

Question 23

Interaction during gait continued…

Answer 23

 Later in the stance phase of gait the ankle-foot
complex supinates and this “locks” the transverse
joint and causes the foot to become more rigid
 Active toe extension (particularly when combined
with plantar flexion) pulls the plantar aponeurosis
taut and further stabilises the foot
 Now that the foot is a rigid lever, force from muscles
such as gastrocnemius and soleus can be effectively
transferred from the achilles tendon, through the
midfoot, to the metatarsal heads during propulsion