{
 "serie": "s201_STIR_SAG",
 "n_imgs": 18,
 "s": 51.0,
 "respuesta": "**Series: Sagittal STIR, right ankle/foot (lateral → medial)**\n\n**Bones / marrow**\n- **Talus – body, inferior/central (slices 10–12):** rounded focus of high STIR signal within the talar body adjacent to the posterior subtalar facet, with a smaller bright focus in the dome region on slice 8. Appearance suggests subchondral cyst formation / bone marrow oedema of the talar body, possibly related to posterior subtalar joint degeneration or a contusion. Confidence: medium.\n- **Calcaneus, tibia, fibula, navicular, cuboid, cuneiforms, metatarsals:** no convincing marrow oedema or fracture line. Confidence: medium (limited by noise on far-medial/lateral slices).\n\n**Joints / fluid**\n- **Tibiotalar joint effusion (slices 9–12):** fluid distending the anterior and posterior tibiotalar recesses; fluid also seen in the medial gutter (slices 12–13). Small-to-moderate effusion. Confidence: high.\n- **Posterior subtalar joint (slices 8–11):** fluid signal within the joint and extending into the **sinus tarsi**, where the normal fat is replaced by high signal (slices 6–8) – sinus tarsi oedema/synovitis, possibly with interosseous ligament sprain. Confidence: medium.\n- Talonavicular / midfoot joints: no significant effusion. Retrocalcaneal bursa: no more than trace fluid. Confidence: medium.\n\n**Tendons**\n- **Peroneal tendons (slices 4–6):** two parallel linear structures descending obliquely posterolateral to the calcaneus surrounded by bright fluid signal – peroneal tenosynovitis. Fluid/oedema continues along the plantar-lateral midfoot into the cuboid tunnel region (slices 5–7), consistent with peroneus longus sheath fluid ± adjacent soft-tissue oedema. No definite tendon split or discontinuity identified on these slices. Confidence: medium.\n- **Medial tendons (tibialis posterior / FDL, slices 13–14):** thin rim of fluid around the tendons behind the medial malleolus – mild tenosynovitis. Confidence: low–medium (partly noise‑degraded).\n- **Achilles tendon (slices 8–11):** normal thickness and low signal; Kager fat pad clear. Confidence: high.\n- Anterior extensor tendons: unremarkable. Confidence: medium.\n\n**Ligaments**\n- **Lateral ligament complex (slices 5–7):** ill-defined high signal in the soft tissues anterior and inferior to the lateral malleolus (ATFL/CFL region) suggesting lateral ligament sprain/oedema; discrete ligament fibres not well resolved in this plane. Confidence: low–medium.\n- Deltoid ligament: oedema around medial malleolus (slices 13–14), possible sprain. Confidence: low.\n- Spring ligament, plantar fascia: plantar fascia origin shows linear high signal along its plantar surface (slices 6–8) – possible mild plantar fasciitis / peri-fascial oedema; nonspecific. Confidence: low.\n\n**Soft tissues**\n- **Plantar / midfoot soft-tissue oedema (slices 5–7):** extensive high signal in the plantar soft tissues beneath the cuboid and anterior calcaneus, between the plantar muscles, beyond what would be expected from the peroneal sheath alone – soft-tissue oedema (post-traumatic vs inflammatory). Confidence: medium.\n- Mild diffuse subcutaneous oedema over the dorsolateral foot and around the ankle. Confidence: medium.\n- Scattered bright tubular structures on far-medial slices (14–16) are most consistent with vessels; no focal collection.\n\n**Impression**\n1. Tibiotalar joint effusion with posterior subtalar joint fluid and sinus tarsi oedema.\n2. Subchondral cyst/marrow oedema in the talar body adjacent to the posterior subtalar joint.\n3. Peroneal tenosynovitis with plantar-lateral midfoot soft-tissue oedema; mild medial (tibialis posterior/FDL) tenosynovitis.\n4. Probable lateral ligament complex sprain; possible mild deltoid and plantar fascial oedema.\n5. Achilles tendon and remaining osseous structures normal."
}