ULTRASOUND OF THE FOOT - Pathology

For normal anatomy and scanning protocol

Plantar Fascia

• Plantar Fasciitis
• Plantar fascial tears
• Plantar fibromatosis

Plantar Fascitis

A thickened plantar fascia origin (red arrows) compared to a normal plantar fascia on the right.	The red arrows indicate the margins of the thickened plantar fascia. Note the convex shape and hypoechoic change.

Plantar Fascial Tear

A large partial tear of the plantar fascia. There is a surroinding haematoma and inflammation (red). The irregular outine and disrupted fibres are  visible (green)	Increased vascularity of the plantar fascia tear and surrounding tissues.

Plantar Fibromatosis

• Plantar fibromatoses are fusiform nodular thickenings of the plantar fascia in the mid foot.
• Patients will usually present with one or more palpable lumps or thickenings in the arch of their foot.
• Not usually painful but may be symptomatic due to physical discomfort.

Scan plane for plantar fibromatosis	A small nodule in the superficial surface of the plantar fascia.

The fusiform hypoechoic nodule (purple) with typical disruption to the uniform fibrillar achitecture of the Plantar fascia (yellow).	Always scan right  along the plantar fascia. There are usually more nodules than are palbable. (Note the mirror image artefact deep to the nodule)

A panoramic image (or 'extended field of view') of Plantar fibromatosis.

Plantar Wart (Verucca Plantaris)

• Can occur anywhere on the sole of the foot or toes.
• Is the human pappiloma virus

Typical appearance of a plantar wart. Rounded deep bulging of the cutaneous layers with posterior enhancement and rich deep vascularity.

Bones and Joints

Assess the extensor tendons dynamically for pathology. Check the underlying joints (with minimal probe pressure) for effusions.

View each joint and extensor tendon.	Insert caption here

Degenerative arthritis of the 3rd tarso-metatarsal joint. The markedly increased vascularity using power doppler indicates acute inflammation.	On power doppler, marked hyperaemia is isolated to the Navicular-Cuneiform joint indicating focal, acute inflammation. The Talo-navicular joint is shows no increased vascularity.

The mixed echogenic appearance of  calcific tophus of gout arising out of the 1st MTPJ.	The gout extends out over the plantar aspect of the Flexor Hallucis Longus tendon. Differential diagnosis is Calcium pyrophosphate deposition disease (CPDD)

Xray showing the osteophytic lipping of the navicular-cuneiform joint.	Ultrasound shows the bony irregularity and associated synovial cysts and thickening.

Morton's Neuroma

To differentiate a neuroma from a bursa:
A Mortons neuroma will be non compressible and should have subtle internal vascularity. Utilise the Mulder's manouvre to correlate the click and symptoms with the pathology found.

The non compressible large Neuroma with internal vascularity visible on color doppler.	Mortons neuroma

Inter-Metatarsal Bursa

• A common cause of forefoot neuralgia.
• A thin bursa located between each metattarsal head.

The same scan plane and technique is employed to examine for Mortons neuromas or metatarsal bursae because they are differential diagnoses for each other.	The bulging bursa seen from the plantar aspect with dorsal counter-pressure applied. Be careful not to apply too much transducer pressure which will prevent visualisation of the bursa.

In longitudinal, the bursa can be seen to protrude out the plantar aspect between the metatarsal heads	A large, bulging intermetatarsal bursa, clinically mimicking a Morton's neuroma.

Loculated bursal fluid with bursal thickening.	The bursa being compressed. The probe is on the plantar aspect and counter-pressure applied with a finger in the dorsal inter-metatarsal space.

'Interstial Bursa' under the 1st metatarso-phalangeal joint. Similar to the olecranon bursa in the elbow, usually it will be only mildy tender but presents as an inconvenient swelling. It Is important to clinically exclude infection or gout.

Plantar Plates

The plantar plates are the fibrocartilage labrum arising from the base of the proximal phalanx, plantar aspect.

Scan plane to assess the plantar plate. Move sideways to view each metatarso-phalangeal joint.	A normal plantar plate (green) underlying the flexor digitorum tendon.

Calcification along the plantar surface of the 2nd plantar plate.	Hypoechic degenerative change in the 3rd plantar plate.

Degenerative plantar plate	Ultrasound of a joint effusion elevating the plantar plate.

Foreign Bodies

• Ultrasound is very effective at identifying foreign bodies.
• It is important to note the direction of travel, depth from the skin and relationship to other anatomy (vascular etc)

A date-palm thorn in the foot.	A video clip showing the highly mobile thorn that has speared the anterior tibio-fibula ligament.