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asktheexpert
understanding ankle ultrasound
BY LISA BRIGGS, AMS, CANBERRA IMAGING GROUP, ACT.
Dear expert, I rarely perform musculoskeletal ultrasound at my workplace but we have
recently had a number of patients present for ankle examinations. Where do I begin?
What are we to examine?
A thorough knowledge of ankle anatomy
is necessary before attempting any
examination of this area.
inserting onto bone. When scanned in the
transverse plane tendons appear ovoid in
shape. Most tendons have a tendon sheath
except for the Achilles tendon.
Before beginning, the sonographer should
take on a clinician’s role and establish the
region to be examined and the surrounding
areas to be observed. One should note the
patient’s movements, whether restricted or
not, the gait of the patient as the region of
interest is in the lower limb, as well as taking
a thorough clinical history from the patient.
Anatomy of the ankle
Become observant
The ankle joint is complex and is made up
of two joints: the true ankle joint and the
subtalar joint.
The ankle is a very complex region to
examine. It is imperative to differentiate
the ultrasonic appearances of ligaments,
tendons, nerves and surrounding
anatomy. This is the basic principle of
musculoskeletal (MSK) scanning and once
the sonographer has a firm knowledge of
these structures and their appearance the
next step is to understand their functions.
A ligament by definition is a short band
of tough, fibrous, connective tissue
composed mainly of long, stringy, collagen
fibres. They join bone to bone and in
the ankle enforce and reinforce stability.
Ultrasonically, ligaments are seen as bright
echogenic bands.
A tendon by definition is a tough band of
fibrous, connective tissue that connects
muscle to bone, or muscle to muscle,
and is designed to withstand tensile
forces. Tendons are similar to ligaments
except that ligaments join one bone to
another. Tendons and muscles work
together and can only exert a pulling force.
Ultrasonically their appearance is that of a
larger bright band exiting from muscle and
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The ankle is divided into four basic sections:
tibialis anterior t.
extensor digitorum longus t.
extensor hallucis
longus t.
• Anterior ankle
• Medial ankle
lateral
malleolus
• Lateral ankle
calcaneus
• Posterior ankle
The true ankle joint is composed of three
bones:
peroneus
tertius t.
peroneus
brevis t.
Fig 1. Anatomy of the anterolateral ankle.
(t.=tendon)
1. The tibia which forms the medial
portion of the ankle.
• Fibula
2. The fibula which forms the lateral
portion of the ankle.
• Talus
3. The talus inferiorly.
The true ankle joint is responsible for
dorsi- and plantar-flexion (up-and-down
motion) of the foot.
The subtalar joint is inferior to the true ankle
joint and consists of the talus superiorly and
calcaneus inferiorly. The subtalar joint is
responsible for inversion and eversion
(side-to-side motion) of the foot.
The anterolateral ankle
The anterolateral ankle (fig 1) contains a
number of bony landmarks and soft tissue
structures.
Bony landmarks of the lateral ankle
include the:
peroneus
longus t.
• Calcaneus
• Cuboid
The soft tissue structures identified at the
anterior ankle level are:
• Tibialis anterior tendon
• Origin:
–
lateral tibial condyle
– proximal two-thirds of
anterolateral surface of tibia
– interosseous membrane
– anterior intermuscular septum and
crural fascia
• Insertion:
– medial and plantar surface of
base of first metatarsal
soundeffects
understanding ankle ultrasound
– medial and plantar surface of
the cuneiform
• Action:
• Peroneus tertius tendon
(not usually examined)
• Origin:
– strongest dorsiflexor
– distal third of anterior fibula
– inverts and adducts the foot
– distal and lateral aspect of
extensor digitorum muscle
• Blood supply: anterior tibial artery
• Nervous supply: deep peroneal
nerve, lumbar nerves four and
five as well as sacral nerve one.
• Extensor digitorum longus tendon
• Origin:
– lateral tibial condyle
– superior anterior surface of fibula
– interosseous membrane
– crural fascia
• Insertion:
– dorsal surface of the bases of the
middle and distal phalanges of
the second through fifth rays
– via four tendons and giving a
fibrous expansion
• Action:
1. extends the lateral four toes
2. weak dorsiflexor and everts foot
• Blood supply: anterior tibial artery
• Nervous supply: deep peroneal
nerve, lumbar nerves four and
five as well as sacral nerve one.
• Extensor hallucis longus tendon
• Origin:
– medial aspect of the fibula
• Insertion
– dorsal surface of base of fifth
metatarsal
• Action:
– extends the fifth toe
– weak dorsiflexor and everts foot
• Blood supply: anterior tibial artery
• Nervous supply: deep peroneal
nerve, lumbar nerves four and five
as well as sacral nerve one.
– head of the fibula
– proximal two-thirds of lateral fibula
– weak dorsiflexor
– weak inversion and adduction
• Blood supply: anterior tibial artery
• Nervous supply: deep peroneal
nerve, lumbar nerves four and five as
well as sacral nerve one.
soundeffects
Fig 3. Lateral ankle diagram.
– adjacent intermuscular septum
• Insertion:
– plantar surface of cuboid
– base of the first and second
metatarsals
– plantar surface of medial
cuneiform
• Action:
– weak plantarflexion of the foot at
the transverse tarsal joint
– extends distal phalanx of hallux
talofibular
ligament
• Origin:
– crural fascia
• Action:
calcaneofibular
ligament
• Peroneus longus tendon (fig 2)
– eversion and abduction of the foot
– dorsal surface of base of proximal
and distal phalanx of hallux
(great toe)
tibiofibular
ligament
The soft tissues examined at the lateral
aspect of the ankle include the following:
– interosseous membrane
• Insertion:
Fig 2. Transverse image of the peroneal tendons
(longus and brevis) and retinaculum.
• Blood supply: muscular branches of
the peroneal artery
• Nervous supply: superficial peroneal
nerve, lumbar nerves four and five as
well as sacral nerve one.
• Peroneus brevis tendon (fig 2)
• Origin:
– distal two-thirds of lateral fibula
– posterior and anterior
intermuscular septum
• Insertion:
Fig 4. Transverse image of normal tibiofibular ligament.
– tuberosity on lateral aspect of
base of fifth metatarsal
• Action:
– eversion and abduction of the foot
– weak plantarflexion of foot
• Blood supply: muscular branches
of the peroneal artery
• Nervous supply: superficial peroneal
nerve, lumbar nerves four and five
as well as sacral nerve one.
The ligamentous attachments (fig 3)
examined at the lateral ankle are:
• the anterior tibiofibular ligament (fig 4)
(connecting the tibia to the fibula)
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understanding ankle ultrasound
• the talofibular ligament (connecting talus
to the fibula)
• the lateral collateral ligaments (attaching
the fibula to the calcaneus which
provide lateral ankle stability).
The medial ankle
Medial ankle bony landmarks include:
• Tibia
• Calcaneus
• Navicular
• First cuneiform
The soft tissues examined on the medial
aspect of the ankle (fig 5) are:
• Tibialis posterior tendon
• Origin:
– posterior, proximal tibia
– interosseous membrane
– medial surface of fibula
• Insertion:
– navicular tuberosity (principal)
– all three cuneiforms (plantar
surface)
– bases of second-fourth
metatarsals
– cuboid
– sustentaculum tali of calcaneus
• Action:
– stabilises ankle
– inversion and adduction of foot
– prevents hyperpronation while
in gait
– weak plantar-flexion of ankle
• Blood supply: peroneal artery and
posterior tibial artery
• Nervous supply: tibial nerve, lumbar
nerve five and sacral nerve one.
• Flexor digitorum longus tendon
• Origin:
– posterior surface of tibia
– crural fascia
• Insertion:
– plantar surface of bases of the
second-fifth distal phalanges
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• Action:
tibialis anterior t.
– primarily flexes second-fifth toes
– weak plantar-flexion
– weak inversion and adduction
of foot
• Blood supply: peroneal artery and
posterior tibial artery
tibialis posterior t.
flexor digitorum
longus t.
extensor hallucis
longus t.
• Nervous supply: tibial nerve, lumbar
nerve five and sacral nerve one.
bursa
flexor hallucis
longus t.
• Flexor hallucis longus tendon
(posterior)
• Origin:
Achilles t.
Fig 5. Anatomy of the medial ankle. (t.=tendon)
– posterior, inferior two-thirds of
fibula
– interosseous membrane
– crural fascia and posterior
intermuscular septum
• Insertion:
– plantar surface of distal
phalanx of hallux
• Action:
– flexes hallux
posterior talotibial ligament
talonavicular ligament
second dorsal
cuneonavicular
ligament
medial
talocalcaneal
ligament
deltoid
ligament
first dorsal
cuneonavicular
ligament
– weak plantar-flexion of the foot
– weak inversion and adduction
of foot
• Blood supply: peroneal artery and
posterior tibial artery
• Nervous supply: tibial nerve, lumbar
nerve five and sacral nerves one
and two.
• Deltoid ligament complex –
superficial and deep fibres
• Superficial fibres:
– anterior (tibionavicular)
– middle (calcaneotibial)
medial
cuneonavicular
ligament
articular
capsule
long
plantar
ligament
plantar
calcaneonavicular
posterior
ligament
talocalcaneal
ligament
calcaneocuboid
ligament
Fig 6a. The deltoid ligaments.
– posterior fibres (posterior
talotibial)
• Deep fibres:
– Anterior talotibial
Figure 6a demonstrates the anatomy
of the deltoid ligament complex.
Note that the whole of the deltoid
ligament complex is difficult to visualise
due to the direction of the ligamentous
attachments. The deltoid ligament
complex lies deep to the tibialis posterior
and flexor digitorum longus tendons.
Fig 6b. Comparative transverse images of the deltoid
ligament complex. Right is normal and the left
demonstrates a partial tear (arrows).
soundeffects
understanding ankle ultrasound
Figure 6b demonstrates comparative
transverse images of the deltoid ligament
complex. The right side is normal while the
left demonstrates a partial tear.
The posterior ankle
The major bony landmark of the posterior
ankle is the calcaneus.
Soft tissue structures examined at the
posterior ankle (fig 7) include:
• Achilles tendon
• Origin:
– the gastrocnemius and the soleus
muscles
• Insertion:
– calcaneus
• Action:
– plantar-flexion of the foot with
the gastrocnemius and soleus
muscles
• Blood supply: two supplies are noted:
surrounding muscles to the Achilles
tendon; and distal tendon/bone
interface at the insertion.
• Soleus muscle
• Origin:
– proximal fibula
– soleal line of tibia
• Insertion:
– calcaneus via the medial portion
of the Achilles tendon
• Action:
– plantar-flexion of the foot
• Blood supply: sural branches of
popliteal artery, muscular branches
of peroneal artery and posterior
tibial artery
• Nervous supply: tibial nerve and
sacral nerves one and two.
• Gastrocnemius muscle
• Origin:
– medial head: just superior to
medial condyle of femur
– lateral head: just superior to
lateral condyle of femur
• Insertion:
– calcaneus via the lateral portion of
the Achilles tendon
soundeffects
• Action:
medial
gastrocnemius
muscle
– plantar-flexion of the foot
– knee flexion (when not weight
bearing)
– stabilises ankle and knee when
standing
• Blood supply: sural branches of
popliteal artery, muscular branches
of peroneal artery and posterior
tibial artery
• Nervous supply: tibial nerve and
sacral nerves one and two.
• Plantaris muscle
(not present in every patient)
• Origin:
– superior to lateral head of
gastrocnemius on femur
lateral
gastrocnemius
muscle
Achilles tendon
calcaneus
Fig 7. Anatomy of the posterior lower limb
demonstrating the Achilles tendon and surrounding
structures.
• Insertion:
– calcaneus, medial to the Achilles
tendon, or blending with the
calcaneal tendon
• Action:
– like a weak gastrocnemius muscle
• Blood supply: sural branches of
popliteal artery, muscular branches
of peroneal artery and posterior
tibial artery
• Nervous supply: tibial nerve and
sacral nerves one and two.
Bursa – superficial and deep
• Retrocalcaneal bursa (fig 8) – lies
deep to the Achilles tendon between
the tendon and calcaneus.
• Subcutaneous calcaneal bursa
(Achilles bursa) – located between
the skin and distal Achilles tendon
over the calcaneus.
Ultrasound technique
The ultrasound examination of the ankle
is usually a targeted one; however, the
musculotendinous junction and insertion
of the tendon/tendons also need to be
examined.
A high frequency probe, greater than
12 MHz, is essential when performing MSK
ultrasound as the examined structures are
predominantly superficial. ‘Hockey stick’
transducers are ideal as they are easier to
retrocalcaneal bursa
Fig 8. The anatomy of the posterior ankle
demonstrating the retrocalcaneal bursa.
manage and the footprints are smaller.
The use of an offset (stand off) is advisable
for imaging superficial structures and aids
contact in hard-to-access areas such as
the lateral malleolus. A thick coupling gel
may be used as it acts as an offset and
does not run.
In general, the examination should include
comparative images of the unaffected
side as they are beneficial for diagnosis
(determining normal and abnormal
appearances). In addition the use of colour
Doppler imaging (fig 9) is important to
demonstrate hyperaemia within a tendon or
when trying to determine whether there is a
tear present. It is important
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understanding ankle ultrasound
to decrease transducer pressure when
employing colour Doppler as flow is very
slow and small infiltrating vessels will be
compressed.
The area of concern is scanned firstly in
the transverse plane.
Fig 9. Longitudinal colour Doppler image of posterior
tibialis tendon with partial tear and evidence of
neovascularisation.
Fig 10. Dual screen image of anterior tibial tendon
rupture (image orientation right – transverse and left
– longitudinal).
In the lateral ankle routinely look at the
point of interest. Comparative imaging is a
valuable tool when looking for tendon size,
shape and position.
The peroneal tendons are routinely
examined from distal fibula to insertions.
As stated previously the peroneus brevis
inserts onto the base of the fifth metatarsal
and as such this should be examined in
its entirety. The peroneus longus dives
deep into the plantar aspect of the foot and
should also be examined in its entirety.
The most common pathologies seen in
association with these tendons are:
• Tendonitis/tendinosis.
• Tenosynovitis as these tendons have a
tendon sheath.
Fig 11a. Panoramic images of the Achilles tendon –
partial tear.
Fig 11b. Panoramic images of the Achilles tendon
– complete rupture.
• Partial or full thickness tendon tears
(figs 10 and 11). If a full thickness tear
is demonstrated the rupture site must
be measured. The level of retraction
(fig 12) is to be noted as well as
documentation of how far from the
insertion site the tear occurs.
• Grade I is an injury without macroscopic
tears. No mechanical instability is noted.
Pain and tenderness is minimal.
• Grade II is a partial tear. Moderate
pain and tenderness is present.
Mild-to-moderate joint instability
may be present.
• Grade III is a complete tear (fig 13b).
Severe pain and tenderness, inability
to bear weight, and significant joint
instability are noted.
When examining the medial aspect of the
ankle a thorough history from the patient
is essential in determining where to begin
the examination. For example, if a patient
presents with medial pain and no apparent
injury one would ask the question “Is
this (a) a mechanical problem, (b) due to
arthritic change or (c) attributable to some
other cause/pathology?”.
If pain is the result of a mechanical
problem for example, a change of gait,
increase in weight, decreased exercise,
etc., the sonographer should concentrate
on the posterior tibialis tendon. This tendon
inserts predominantly onto the navicular
and helps form the arch of the foot. If the
arch has dropped or flattened one should
image the insertion of the posterior tibialis
tendon. Abnormal appearances at the
insertion or just proximal to this include
• Dislocation/subluxation of the peroneus
brevis at the level of the lateral
malleolus. Stress views are used to
substantiate these findings. It is also
necessary to identify the superior/
inferior peroneal retinaculum at the
level of the lateral malleolus.
Examination of lateral ligamentous injuries
is the most common reason that the
sonographer will be asked to perform an
ultrasound of the ankle joint. Inversion
injuries of the ankle account for 40%
of all athletic type injuries. The anterior
talofibular ligament (ATFL) (fig 13) and
the calcaneofibular ligament (CFL) are
sequentially injured when a plantar-flexed
foot is forcefully inverted (strained ankle).
Fig 13a. Longitudinal image of a normal intact
talofibular ligament.
The posterior talofibular ligament (PTFL)
is rarely injured, except in association
with a complete dislocation of the talus.
Fig 12. Panoramic image of anterior tibial tendon
rupture with retraction.
24 issue 1, 2007
Ligamentous injuries of the ankle
are classified into the following three
categories depending on the extent of
damage to the ligaments:
Fig 13b. Longitudinal image of a ruptured talofibular
ligament.
soundeffects
understanding ankle ultrasound
increased tendon size, hypoechogenicity,
presence/absence of hyperaemia and bony
degeneration with intrasubstance tears.
In the case of medial dislocation or trauma the
examination should be targeted to the deltoid
ligament complex. This is a challenging area
to scan due to the direction and different
insertions of the ligaments that make up
this complex. Generally the calcaneotibial
ligament (middle portion) is what is imaged.
This portion lies deep to the posterior tibialis
and flexor digitorum tendons. From its tibial
attachment it inserts onto the entire length of
the sustentaculum tali of the calcaneus.
The most common pathologies seen in
relation to the ankle joint include:
• Tendonitis/tendinosis.
• Tenosynovitis; with or without
hyperaemia.
• Tears; partial or full thickness.
• Systemic changes such as gout,
arthritis, inflammation, etc.
• Tendon/bone changes.
• Soft tissue changes.
• Bursitis (fig 14).
• Avulsion fractures with tendon disruption.
• Musculotendinous junction tears.
Conclusion
Ultrasound is a very thorough way
of examining the ankle joint and the
surrounding structures. Assessment of plain
soundeffects
• Check the patient’s gait, stance, and the
way in which they weight bear.
• Ask what symptoms they are
experiencing.
• Is their injury/complaint due to trauma,
pain, work, etc?
Fig 14. Longitudinal image of retrocalcaneal bursitis.
Bursitis with calcification at the Achilles tendon
insertion.
films are invaluable before commencing
the examination as they will help determine
any bony changes that may influence
the direction of the examination – such
as assessing for avulsion fractures,
calcification or arthritic changes in joint
articulations. Although magnetic resonance
imaging (MRI) may be the study of choice
for examining the ankle joint as a whole,
ultrasound is very good when examination
of the soft tissue structures is required. We,
as sonographers, must take a clinician’s
perspective in establishing the region of
interest to be examined and the way in
which it will be examined. It is essential to
have a thorough knowledge of the anatomy
and functions of the area/s of concern and
in turn this helps in making diagnosis easier
and the examination more thorough.
Points to note before and during the
examination:
• Observe the patient as they walk in for
their examination.
• Implement dynamic scanning –
stress the region of interest.
• Get the patient involved in the
procedure so you can induce
symptoms.
• Target-scan the area.
• Use colour Doppler imaging to show
pathology such as hyperaemia.
Recommended reading/resources
• Taylor M. Talofibular ligament injury.
emedicine [database on the internet].
c 2006 [updated 2005 Dec 9; cited 2006
Dec 19]. Available from: http://www.
emedicine.com/sports/topic126.htm.
• Wheeless’ Textbook of Orthopaedics
[homepage on the internet]. c 2005
[cited 2006 Dec 19]. Available from:
http://www.wheelessonline.com.
• The Hosford Muscle Tables: Skeletal
Muscles of the Human Body.
[homepage on the internet]. c 1998
[cited 2006 Dec 19]. Available from:
http://www.ptcentral.com/muscles.
Acknowledgements
Julie Wheatley for the anatomical illustrations.
issue 1, 2007 25