Patient History

60-year-old woman with no known injury complaining of left ankle pain.

Findings

SKELETAL/BONES:

Retrofibular groove is convex posteriorly (loss of the normal convex morphology of the retrofibular groove). No fracture, reactive osteoedema, or focal aggressive osseous abnormality.

ARTICULATIONS:

Tibiotalar joint/talar dome: No osteochondral defect of the talar dome or tibial plafond.

Ankle mortise/syndesmosis: The ankle mortise is in anatomic alignment. No syndesmosis widening.

Chopart joint: Unremarkable.

Midfoot/hindfoot: No fracture or injury of the anterior calcaneal process. No prominent midfoot or hindfoot arthrosis.

Lisfranc joint: The Lisfranc joint is intact, without fracture or joint space widening.

LIGAMENTS:

High ankle: Dissecting capsular cyst (less likely ganglion pseudocyst), with tail arising from the tibiotalar articulation and stem ligament near the anterolateral gutter, dissecting into the interosseous space (measuring approximately 2.5 cm). High ankle ligaments intact.

Low ankle: Intact.

Subtalar/Chopart: Intact.

TENDONS:

Large, complex, split-tear of the retro- and inframalleolar peroneus brevis with associated reactive tenosynovitis. A cystic, concealed intertendinous component extends down to the insertion at the base of the 5th metatarsal. Tear measures approximately 5.5 cm in total length. Moderate-sized sheath effusion with distension.

Peroneus longus intact.

Extensor and flexor tendons intact and unremarkable.

Achilles tendon intact. Minimal distal paratenon thickening.

GENERAL:

Sinus tarsi: Small stem ligament bursal cyst. Otherwise unremarkable.

Muscles: No traumatic muscle injury. No volumetric muscle atrophy.

Soft tissue:  Swollen but intact peroneal retinaculum, particularly anteriorly.

Plantar fascia: Intact.

Neurovascular complex/tarsal tunnel: Unremarkable. No evidence of entrapment neuropathy.

Intra-articular/loose bodies: None.

Impressions

  1. Large juxtamalleolar/inframalleolar peroneus brevis complex split tear, with cystic interstitial extension distally, measuring approximately 5.5 cm in length.
  2. Dissecting capsular cyst (less likely ganglion cyst) with tail appearing to arise from the anterolateral aspect of the tibiotalar articulation/stem ligament bursa (dissecting the distal tibiotalar interosseous space and membrane). High ankle ligaments intact.