Foot pathology

Plantar Fascia

  • Plantar Fasciitis
  • Plantar fascial tears
  • Plantar fibromatosis

Plantar Fasciitis

Ultrasound image- A thickened plantar fascia origin (red arrows) compared to a normal plantar fascia on the right.

Ultrasound image- The red arrows indicate the margins of the thickened plantar fascia. Note the convex shape and hypoechoic change.

Plantar Fascial Tear

Ultrasound image- Increased vascularity of the plantar fascia tear and surrounding tissues.

Ultrasound image- 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)

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Mucoid degeneration

  • This occurs when there is irreversible damage to a tendon or ligament with mucinous material excreted from cells within the tendon matrix filling the void.
  • Mucoid degeneration on a tendon or ligament is generally painful and is dysfunctional. 

 

Plantar Fibromatosis

Plantar fibromatosis nodules on the plantar fascia

  • 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.

Ultrasound image- A small nodule in the superficial surface of the plantar fascia.

Ultrasound image-The fusiform hypoechoic nodule (purple) with typical disruption to the uniform fibrillar achitecture of the Plantar fascia (yellow).

Ultrasound image-Always scan right along the plantar fascia. There are usually more nodules than are palbable.
(Note the mirror image artefact deep to the nodule)

Ultrasound image-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

Ultrasound image- 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.

Ultrasound image- Effusion and synovial thickening

Ultrasound image- Degenerative arthritis of the 3rd tarso-metatarsal joint.
The markedly increased vascularity using power doppler indicates acute inflammation.

Ultrasound image- 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.

Ultrasound image- The gout extends out over the plantar aspect of the Flexor Hallucis Longus tendon.
Differential diagnosis is Calcium pyrophosphate deposition disease (CPDD).

Ultrasound image- The mixed echogenic appearance of calcific tophus of gout arising out of the 1st MTPJ.

Ultrasound image shows the bony irregularity and associated synovial cysts and thickening.

Xray showing the osteophytic lipping of the navicular-cuneiform joint.

Morton's Neuroma and intermetatarsal bursitis

To differentiate a neuroma from a bursa:

  • A Mortons neuroma will be non compressible and may have subtle internal vascularity.
  • A neuroma will lie at the plantar aspect of the metatarsal head/neck.
  • If the pathology seen lies between the metatarsal heads, it is likely bursal in origin, not a neuroma.
  • With high frequency, quality equipment, the nerve can be identified an assessed directly for a focal thickening.
  • Utilise the Mulder’s manouvre to correlate the click and symptoms with the pathology found.

Longitudinal ultrasound view of a Morton’s neuroma.
The nerve is indicated by the white arrows.
Note the subtle fusiform thickening (yellow highlight). The video below demonstrates the same neuroma being impinged by an underlying intermetatarsal bursa.
(image courtesy of R. McNicol)

The non compressible large Neuroma/bursal complex with internal vascularity visible on color doppler ultrasound.

Mortons neuroma ultrasound image.

A Morton’s neuroma and intermetatarsal bursa.

The bursa is seen extruding out from between the metatarsal heads to impinge upon the neuroma.

(Image courtesy of R. O’Hea)

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.

Ultrasound image- 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.

Using a modified ‘Mulder’s manouver, the thickened intermetatarsal bursa can be seen extruding out the plantar aspect of the foot. This elicits a palpable click and reproduces the patient’s symptoms. This is not a Morton’s neuroma but can produce similar symptoms.

Ultrasound in longitudinal, the bursa can be seen to protrude out the plantar aspect between the metatarsal heads.

Ultrasound image- A large, bulging intermetatarsal bursa, clinically mimicking a Morton’s neuroma.

Ultrasound image- 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.

Adventitial Bursae

  • Not  true anatomical bursae.
  • Coalescence of interstitial oedema into a semi-contained collection.
  • Uusually complex and may be ill defined related to their non capsular nature.
  • Thought to be recurring secondary to compressive/frictional forces.
  • Most commonly seen in the subcutaneous fat. Plantar surface of the ball of the foot across the level of the metatarsal heads (1-3). Also around the medial aspect of the 1st MTPJ (bunion patients)
  • May be hyperaemic.

Ultrasound image- ‘Interstitial 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.

Ultrasound image- Adventitial Bursitis
Superficial swelling under the foot.

Plantar Plates

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

Ultrasound scan plane to assess the plantar plate. Move sideways to view each metatarso-phalangeal joint.

Ultrasound image- A normal plantar plate (green) underlying the flexor digitorum tendon.

Ultrasound image- Calcification along the plantar surface of the 2nd plantar plate.

Ultrasound image- Hypoechic degenerative change in the 3rd plantar plate.

Ultrasound image- 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).

Ultrasound image- A date-palm thorn in the foot.