ankle normal
lateral ankle
- peroneus longus and brevis tendons
- calcaneo-fibula ligament
- anterior talofibula ligament
- tibio-fibula ligament
- subtalar joint
peroneus longus & brevis tendons
peroneus longus and brevis tendon scan plane (transverse).
peroneus longus and brevis tendons.
transverse plane at the lateral malleolus.
scan plane for ultrasound of the peroneus brevis tendon insertion to the base of the 5th metatarsal.
ultrasound of the peroneus brevis tendon insertion to the base of the 5th metatarsal.
scan plane for ultrasound assessment of the peroneus longus tendon insertion.
to the base of the 1st metatarsal and the medial cuneiform.
ultrasound of the peroneus longus tendon insertion.
calcaneo-fibula ligament (cfl)
ultrasound scan plane for the calcaneo-fubula ligament.
dorsiflex the foot.
probe position from the anterior lateral malleolus towards the tip of the heel.
ultrasound of the calcaneo fibula ligament.
the peroneus tendons are seen in short axis overlying the ligament.
anterior talo-fibula ligament (atfl)
anatomy of the anterior talofibular ligament.
note that there is a lesser, secondary band inferior to the primary band of the ligament. this has a common origin with the calcaneofibular ligament.
- the atfl runs from the anterior distal fibula to the talus.
- it is the weakest of the lateral ankle ligament complex
tip: plantar-flex and invert the ankle.
ultrasound scan plane for the anterior talofibular ligament (atfl)
important to note there are 2 parallel bands to assess.
ultrasound of the anterior talofibular ligament (atfl)
anterior tibiofibular ligament (tfl)
scan plane for ultrasound of the tibiofibular ligament.
from the atfl, fix the probe on the fibula and rotate the other end of the probe towards the horizontal.
talus will leave the image and tibia will appear. this is when you will visualise the tibiofibular ligament.
ultrasound of the tibiofibular ligament.
the tibia and fibula should be seen as 2 similar ‘hills’.
superficial peroneal nerve
the superficial peroneal nerve (spn) exits the fascia leading to the median and intermediate dorsal cutaneous nerves.
ref: k paraskevas, george & natsis, konstantinos & tzika, maria & ioannidis, orestis. (2013). potential entrapment of an accessory superficial peroneal sensory nerve at the lateral malleolar area: a cadaveric case report and review of the literature.. the journal of foot and ankle surgery : official publication of the american college of foot and ankle surgeons. 53. 10.1053/j.jfas.2013.06.012.
- the superficial peroneal nerve exits the muscle fascia on the lateral lower leg, approximately 10cm proximal to the lateral malleolus. this is a potential area for entrapment.
- it then descends superficially along the fascia to provide branches to the anter-lateral foot and ankle.
ultrasound of the superficial peroneal nerve in the transverse plane.
highlighted ultrasound of the superficial peroneal nerve. a longitudinal plane as it exits the fascia.
anterior ankle
the primary structures to assess anteriorly are:
- tibialis anterior tendon
- extensor digitorum longus tendon
- extensor hallucis longus tendon
- extensor retinaculum
- ankle joint(s)
- deep peroneal nerve
extensor retinaculae
there are 2 extensor retinaculae of the anterior ankle/foot
both overly the extensor tendons acting as pulleys/fulcrum points.
- superior extensor retinaculum: a single broad anchoring band at the level of the distal tibia.
- inferior extensor retinaculum: a slightly y-shaped band. single laterally, dividing into 2 bands laterally. the more proximal inserts onto the tibia, the more distal wraps around to insert onto the planta aponeurosis.
ultrasound appearance:
- hypoechoic 1mm layer overlying the extensor tendons in a transverse plane.
- easily identifiable as you slide down in transverse from the distal tibia.
- the superior will appear, then fade, followed by the inferior retinaculum.
what to look for:
- thickening with or without hyperaemia.
- intact? (complete tears are uncommon)
mechanism of injury:
- hyperextension/plantar flexion injuries
ultrasound scan plane to assess the ankle extensor retinaculum and tendons.
there is a thicker superior retinaculum at the level of the distal tibia and an inferior retinaculum below the ankle crease.
ultrasound of the extensor digitorum tendon and the retinaculum reflecting around it.
tibialis anterior tendon
scan plane to assess the tibialis anterior tendon from the proximal musculo-tendinous junction to the distal insertion.
transverse view of the tibialis anterior tendon at the level of the superior extensor retinaculum.
ultrasound scan plane to assess the tibialis anterior tendon longitudinally.
ultrasound of a normal tibialis anterior tendon – longitudinal plane at the distal tibia.
ultrasound scan plane to assess the tibialis anterior tendon insertion to the base of the 1st metatarsal (and cuneiform).
the distal tibialis anterior tendon curves around the medial arch to it’s insertion.
it is important to follow all the way, particularly patients with a background of degenerative oa.
extensor digitorum and hallucis tendons
deep peroneal nerve
ultrasound scan plane to find the deep peroneal nerve at the anterior ankle.
scan proximally and distally to assess the nerve in transverse.
the nerve accompanies the anterior tibial artery at the distal tibia. as you scan distally in the transverse plane, the nerve is seen to switch from medial to lateral to the artery.
to read a helpful resource for the deep peroneal nerve.
medial ankle
- tibialis posterior tendon
- flexor digitorum tendon
- flexor hallucis longus tendon
- deltoid ligament
- spring ligament
- tibial nerve (and branches)
- deep peroneal nerve.
scan plane to see tibialis posterior, flexor digitorum and flexor hallucis longus tendons (you may need to adjust the probe posteriorly to view the deeper fhl).
ultrasound of tibialis posterior, flexor digitorum and flexor hallucis longus tendons (known as “tom, dick & harry”). if including the neurovascular bundle – tom dick and very nervous harry.
tibialis posterior tendon
ultrasound of the tibialis posterior tendon insertion.
the collagen fibrillar architecture of the tendon becomes speckled by fibro-cartilage as the tendon fibres spread to the various insertional points.
a small accessory ossicle is visible in many patients.(type i accessory navicular bone).
this rounded, embedded ossicle should not be confused with an avulsion
flexor digitorum longus (fdl)and flexor hallucis longus (fhl) tendons
the ‘knot of henry’ where the fhl and fdl tendons cross at the plantar aspect of the posterior arch.
a trace of fluid may normally accumulate here in the fhl sheath. a small percentage of patients may have a communication between the fhl sheath and the ankle joint.
deltoid ligament
the deltoid liagment is a complex piece of anatomy stabilizing the medial ankle joint. due to it’s complexity and oblique fibres, ultrasound cannot entirely exclude pathology, however it is a good positive predictor. (ie ultrasound cannot exclude pathology).
the deltoid ligament is comprised of 4 inter-related ligamentous components.
- posterior tibiotalar ligament.
- tibiocalcaneal ligament
- tibionavicular ligament.
- anterior tibiotalar ligament.
to examine the deltoid ligament with ultrasound, you need to evert and flex the foot to stretch each component individually.
the posterior tibio-talar ligament ultrasound scan plane.
dorsiflex and evert the foot.
deltoid ligament ultrasound.
- the posterior tibio-talar ligament component.
tibio-calcaneal ligament ultrasound scan plane.
dorsiflex and evert the foot.
deltoid ligament ultrasound.
2. the tibio-calcaneal ligament component.
the tibio-navicular ligament ultrasound scan plane.
plantar-flex and evert the foot.
deltoid ligament ultrasound.
3. the tibio-navicular ligament component.
the anterior tibio-talar ligament ultrasound scan plane.
also plantar flex and evert the foot.
deltoid ligament
4.the anterior tibio-talar ligament component
spring ligament (calcaneo-navicular ligament)
this is a technically challenging ligamentous complex to examine with ultrasound.
the spring ligament is comprised of 3 bands which are indistinguishable from one another on ultrasound. posteriorly, the fibres blend with the deltoid ligament.
it runs from sustentaculum talus on the calcaneum to the navicula where it has 3 attachment points.
tibial nerve
distal to the medial malleolus, the tibial nerve divides into the medial and lateral plantar nerves.
a slightly more proximal branch, the medial calcaneal nerve, innervates the superficial area of the heel.
baxters nerve (inferior calcaneal nerve) is the 1st branch off the lateral plantar nerve. entrapment of this nerve may simulate plantar fascitis.
anatomy of the medial ankle, heel and arch nerves.
the tibial nerve bifurcates into the medial calcaneal nerve (posterior) and plantar nerve(anterior).
the plantar nerve then bifurcates into the lateral and medial plantar nerves.
the lateral plantar nerve gives rise to the inferior calcaneal nerve at the posterior arch (this is also called baxter’s nerve).
transverse image posterior and slightly superior to the medial malleolus. this is where the medial calcaneal nerve arises posteriorly from the tibial nerve.
ultrasound scan plane for the tibial and plantar nerves.
tibial nerve bifurcation ultrasound.
transverse image at the infero-posterior arch of the foot showing the subtle bifurcation of the tibial nerve into the plantar nerves.
the medial plantar nerve is anterior.
the lateral plantar nerve is more posterior and then gives rise to the inferior calcaneal nerve (baxter’s nerve)
longitudinal ultrasound of baxter’s (inferior calcaneal) nerve.
this is immediately inferior to the bifurcation of the tibial nerve into the plantar nerves shown in the previous image.
to read a description of baxters nerve pathology on radsource.
scan protocol
role of ultrasound
ultrasound is essentially used for the external structures of the ankle. ultrasound is a valuable diagnostic tool in assessing the following indications; muscular, tendinous and ligamentous damage (chronic and acute) bursitis joint effusion vascular pathology haematomas soft tissue masses such as ganglia, lipomas classification of a mass eg solid, cystic, mixed post surgical complications eg abscess, oedema guidance of injection, aspiration or biopsy relationship of normal anatomy and pathology to each other some bony pathology.
limitations
it is recognised that ultrasound cannot adequately assess the deltoid ligament, the ankle mortice and some inter-tarsal ligments.
patient preparation
- position the patient comfortably where you can readily access the ankle to scan and manipulate.
- this may be supine or seated on the examination bed with feet on the bed.
- alternatively seated on the side of the bed, you seated in front of the ultrasound machine with their foot on your knee.
equipment setup
use of a high resolution, (>10mhz), small footprint probe is essential when assessing the superficial structures of the ankle. careful scanning technique to avoid anisotropy (and possible misdiagnosis). beam steering or compounding can help to overcome anisotropy in linear structures such as tendons. good colour / power / doppler capabilities when assessing vessels or vascularity of a structure. be prepared to change frequency output of the probe (or probes) to adequately assess both superficial and deeper structures.
any assessment of vascularity, the tissue should not be undertension as this may compress the micro-vasculature. ensure light probe pressure and tendons relaxed.
common pathology
- joint effusions.
- tendinopathy and tendon tears
- ligamentosis and ligament tears
- foreign bodies
- oedema
- haematomas
- collections / abscess’
- arthroses / arthritis
scanning technique
lateral ankle
patient sits on the side of a raised bed with foot resting on the sonographers knee for support. alternatively, the patient may sit or lie supine on bed with their foot flat.
peroneus longus and brevis tendons: begin in transverse, posterior to the lateral malleolus. the two tendons are easily seen with the peroneus brevis closest to the bone. follow them proximally to the muscle and distally with particular attention to the insertion of the peroneus brevis tendon onto the base of the 5th metatarsal.
calcaneo-fibular ligament: with the probe diagonally under the malleolus, angled from the fibula to the heel, you will see the peroneus tendons in transverse and the calcaneo-fibula ligament underlying them.
anterior ankle
patient positioned as above.
anterior talo-fibula ligament (atfl): place the heel of the probe on the anterior aspect of the distal fibula and rotate the toe of the probe towards the 2nd toe. the ligament should be readily visible as a 2cm long, 3mm thick tight fibrillar structure.
tibio-fibula ligament (tfl): from the ataf, further rotate the toe of the probe until just above the horizontal. the tfl has a similar appearance to the ataf.
extensor tendons: in transverse across the anterior ankle crease, you will see, from lateral to medial, the extensor digitorum, extensor hallucis and tibialis anterior tendons. by independently mobilising each of the toes and watching the tendons glide, you can identify which is which and exclude tendon rupture the overlying extensor retinaculum should also be observed.
medial ankle
patient positioned as above.
tibialis posterior, flexor digitorum and flexor hallucis longus tendons: assess the tendons along their length in longitudinal and transverse. pay particular attention to the insertion of the tibialis posterior tendon with caution not to mistake the often present accessory ossicle, for an avulsed fragment. begin diagonally under the medial malleolus with the toe of the probe on the malleolus. you will see the tibialis posterior and flexor digitorum tendons in transverse. slide the probe postero-inferiorly and you will see the flexor hallucis longus tendon deeper against the calcaneum.
the deltoid ligament: is poorly assessed with ultrasound.
posterior tibial nerve: the neurovascular bundle is easily seen posterior to the medial malleolus
posterior ankle
patient positioned prone with the feet off the end of the bed.
achilles tendon: perform a survey scan ,in transverse, from the calcaneum up to the musculo-tendinous junction (of both medial and lateral gastrocnemii). rotate into longitudinal and examine for thickening and integrity. at the same time assess the retrocalcaneal (kager’s) fat pad.
the calf muscles and plantaris tendon should also be assessed as clinically indicated.
basic hardcopy imaging
- if undertaking a targeted examination, saved imaging of normal and pathology in 2 planes should be performed.
a comprehensive ankle series should include the following minimum images:
- peroneus tendons – long, trans + peroneus brevis insertion
- calcaneo-fibular ligament
- anterior talo-fibula ligament
- tibio-fibula ligament
- extensor digitorum tendon
- extensor hallucis longus tendon
- tibialis anterior tendon
- tibialis posterior tendon
- flexor digitorum tendon
- flexor hallucis longus
- achilles tendon and retro calcaneal bursa
- document the normal anatomy. any pathology found in 2 planes(ligament tears or thickening, synovial bulging/cysts, joint effusion, gross bony changes), including measurements and any vascularity.