**RIGHT ANKLE MRI**

**Technique:** Axial T1, axial PD fat-saturated, sagittal PD fat-saturated, sagittal T1, and coronal 2D MERGE (T2*-GRE) sequences. No coronal fluid-sensitive spin-echo sequence was obtained; incomplete fat suppression at the periphery of the field of view on the fat-suppressed series (lateral/plantar subcutaneous tissues and supramalleolar posterior compartment) limits assessment in those regions.

**Clinical indication:** Chronic right ankle pain, remote inversion sprain.

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**FINDINGS**

**Joints / effusion / synovium**
- Mild-to-moderate tibiotalar joint effusion distending the anterior and posterior recesses and both medial and lateral gutters (concordant on axial PD FS, sagittal PD FS and coronal MERGE).
- Small posterior subtalar joint effusion.
- Intermediate-signal soft tissue in the anterior tibiotalar recess on T1, more than expected for normal capsule, with corresponding heterogeneous signal on fluid-sensitive images – capsular thickening/synovial scar.
- No intra-articular body confidently identified. A rounded intermediate/low-signal structure posterior to the talar body on one sagittal PD FS slice is not reproduced on the sagittal/axial T1 images, which show a normal posterior talar process and no os trigonum; this most likely represents the posterior tibiotalar/tibiofibular ligament complex and FHL tendon outlined by posterior recess fluid rather than an ossicle or loose body.

**Ligaments**
- *Lateral collateral complex:* The anterior talofibular ligament is not identified as a discrete thin low-signal band on any plane. The anterolateral gutter contains irregular, ill-defined intermediate/high-signal soft tissue with joint fluid tracking into the gutter (axial T1, axial PD FS, sagittal PD FS). Appearance is consistent with chronic ATFL tear with scarring/attenuation and anterolateral gutter synovitis. The calcaneofibular ligament is intact on the visible slices without discrete tear. The posterior talofibular ligament is intact with normal striated morphology.
- *Deltoid complex:* Deep deltoid fibres are mildly thickened/heterogeneous with interposed fluid signal; fibres are continuous without discrete tear – appearance compatible with chronic sprain/scarring.
- *Syndesmosis:* Anterior and posterior inferior tibiofibular ligaments intact. Thin fluid in the tibiofibular recess without widening – physiologic.
- *Sinus tarsi / tarsal canal:* Interosseous talocalcaneal and cervical ligaments are visible and intact. Sinus tarsi fat is predominantly preserved on T1 and MERGE; however, fluid-sensitive sagittal and axial images show hazy high signal and fluid in the lateral sinus tarsi and tarsal canal contiguous with the subtalar joint. Findings indicate mild sinus tarsi synovitis/fluid rather than established fibrotic sinus tarsi syndrome.

**Bones / cartilage / marrow**
- Small focal subchondral high signal at the medial (medial-central) talar dome on sagittal PD FS with corresponding subtle chondral/subchondral irregularity at the medial dome corner on coronal MERGE. T1 marrow signal at this site is preserved and there is no fragment, cystic change or step-off. Appearance is most consistent with a small chondral/early osteochondral lesion (stable, non-displaced).
- Equivocal subchondral irregularity with subtle adjacent high signal along the lateral talar dome on sagittal PD FS only; not confirmed on axial or coronal images or T1. Indeterminate.
- Mild heterogeneous talar body marrow signal on fluid-sensitive images with normal T1 signal – mild reactive edema versus trabecular pattern; no fracture.
- Small anterior tibial plafond osteophyte with subtle contour irregularity of the anterior talar neck – early anterior tibiotalar (kissing) osteophytes.
- Distal tibia, fibula, calcaneus, navicular, cuboid, cuneiforms and metatarsal bases: normal marrow signal, no fracture, cyst or marrow-replacing lesion. Mottled calcaneal signal on MERGE is compatible with normal trabecular pattern. No os trigonum, accessory ossicle or tarsal coalition. Joint spaces preserved; midfoot cartilage intact.

**Tendons**
- *Peroneus longus and brevis:* Normal caliber and signal throughout the retromalleolar groove and along the lateral calcaneus; no split tear, subluxation or dislocation. Small volume of fluid in the common peroneal sheath – mild peroneal tenosynovitis.
- *Flexor hallucis longus:* Tendon intact. Fluid in the FHL sheath at the posteromedial ankle, communicating with the posterior tibiotalar recess – mild FHL tenosynovitis versus decompression of joint fluid.
- *Tibialis posterior and FDL:* Normal caliber and signal; thin sheath fluid halo, likely physiologic.
- *Anterior compartment (tibialis anterior, EHL, EDL):* Normal.
- *Achilles tendon:* Normal thickness and uniformly low signal from myotendinous junction to insertion. No paratendinitis; retrocalcaneal bursa not distended. Kager fat pad normal.

**Plantar structures / soft tissues**
- Plantar fascia of normal thickness at the calcaneal origin; heel fat pad normal.
- Musculature (including FHL belly, abductor hallucis, quadratus plantae, intrinsics) normal on T1 without atrophy, fatty infiltration or mass. Neurovascular bundles normal.
- Homogeneous hyperintensity in the deep posterior compartment/Kager region at the supramalleolar level on the most proximal axial PD FS slices has no correlate on the non-fat-suppressed axial or sagittal T1 images (normal muscle and fat signal, no collection) and coincides with the periphery of the FOV where fat suppression also fails on the sagittal series – attributed to fat-suppression artifact. No mass or ganglion.

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**IMPRESSION**

1. **Chronic anterior talofibular ligament tear with scarring/attenuation and anterolateral gutter synovitis**, in keeping with chronic lateral ankle instability from the remote sprain. CFL and PTFL intact. *(High confidence – concordant on three sequences.)*

2. **Mild-to-moderate tibiotalar effusion with synovitis and small posterior subtalar effusion**, with fluid/synovitis extending into the sinus tarsi and tarsal canal (interosseous ligament intact, fat largely preserved – early/mild sinus tarsi synovitis rather than established sinus tarsi syndrome). *(High confidence for effusion; medium for sinus tarsi synovitis.)*

3. **Small medial talar dome chondral/early osteochondral lesion** without fragment displacement or cystic change (no T1 marrow replacement). Equivocal subtle irregularity of the lateral dome, indeterminate. *(Medium-low confidence; small lesion is a common sequela of inversion injury. Dedicated coronal fluid-sensitive or cartilage-sensitive imaging, or MR arthrography, would better characterize if clinically relevant.)*

4. **Early anterior tibiotalar impingement**: small anterior tibial plafond osteophyte with anterior talar neck irregularity and anterior capsular/synovial thickening. *(Medium-low confidence.)*

5. **Mild peroneal and flexor hallucis longus tenosynovitis**; all tendons intact without tear, split or subluxation. FHL sheath fluid may partly reflect decompression of the joint effusion. *(Medium confidence.)*

6. **Mild deep deltoid ligament thickening/heterogeneity**, compatible with chronic sprain sequela; no discrete tear. *(Low confidence.)*

7. No fracture, marrow-replacing lesion, os trigonum, syndesmotic injury, Achilles or plantar fascia abnormality, or soft-tissue mass. Supramalleolar posterior compartment hyperintensity on axial PD FS is attributed to peripheral fat-suppression artifact (no T1 correlate). *(Medium-high confidence.)*