Tarsal Tunnel Syndrome (Posterior Tibial Tendon Dysfunction)

Radiographic findings may include:

  • increased soft tissue density and volume
  • resorption and/or spur at posterior tibial tendon enthesis
  • tendon calcification
  • accessory navicular

MRI findings may include:

  • posterior tibial tendon enlargement
  • posterior tibial tendon thinning
  • tendon surrounded by high signal intensity
  • high signal intensity within the tendon

Musculoskeletal ultrasound findings may include:

  • posterior tibial tendon enlargement
  • tendon surrounded by hypoechoic signal
  • indistinct margins

Here are presentations of posterior tibial tendon dysfunction:

  • Case 1
  • *Case 1
  • Case 2
  • *Case 2
  • Case 3
  • *Case 3
  • Case 4a
  • *Case 4a
  • Case 4b
  • *Case 4b
mri pttd axial mri pttd sagittal
mri pttd axial marked mri pttd sagittal marked

MRI oblique (but axial) T2 and sagittal T1 images of the posterior tibial tendon (T and arrows). The tendon is enlarged, nearly twice its normal size, and surrounded by fluid (high signal intensity on T2). Diagnosis: tendinosis (Type 1 PTTD).

ptt calcification
ptt calcification marked

DP view. Findings include calcification (C) of the posterior tibial tendon nears its enthesis.

enthesopathy navicular
enthesopathy navicular marked

DP view. Findings include ossicles lateral to the cuboid (gray arrow) and posterior to the navicular tuberosity (black arrow), and spurring at the navicular tuberosity enthesis (white arrow). Diagnoses: os peroneum; accessory navicular type 2; enthesopathy.

us ptt longitudinal
us ptt longitudinal marked

Musculoskeletal ultrasound, longitudinal view of normal posterior tibial tendon (ptt). MM = medial malleolus; Ta = talar head. (Note: the tendon appears hypoechoic on the right half due to anisotropy.)

us ptt axial
us ptt axial marked

Musculoskeletal ultrasound, axial view of normal posterior tibial tendon (ptt). med mal = medial malleolus; fdl = flexor digitorum longus tendon; V = vein; A = posterior tibial artery.

Should a radiographic study be ordered for suspicion of tarsal tunnel syndrome or posterior tibial tendon dysfunction?
Yes. Even though you can't see the tendon itself, other related pathology may be seen, including tendon calcification, tuberosity enthesopathy, accessory navicular, and tuberosity fracture, to name a few.
What are the best views to order?

Order dorsoplantar, lateral, and lateral oblique views.

Musculoskeletal ultrasound and/or MRI are valuable adjunctive studies for assessment of the tendon.

Other information

Anisotropy occurs when the ultrasound transducer is not perpendicular to the structure being imaged, causing it to change in echogenicity.

References:

  1. Resnick, D: Bone and Joint Imaging, 2nd edition, WB Saunders, 1996.
  2. Christman RA: Foot and Ankle Radiology, 2nd edition, Lippincott Williams & Wilkins, 2015.