{
 "serie": "s201_STIR_SAG",
 "n_imgs": 18,
 "s": 47.9,
 "respuesta": "**Right ankle MRI – sagittal STIR (18 slices, medial → lateral)**\n\n**Joint fluid / synovium**\n- Moderate tibiotalar joint effusion distending both the anterior and posterior recesses (slices 8–12), with somewhat irregular/thickened anterior capsular tissue suggesting synovitis or post‑arthroscopic scarring in the anterior gutter. Confidence: high (effusion), medium (synovitis).\n- Fluid in the posterior subtalar joint and increased fluid signal within the sinus tarsi / tarsal canal, best seen on slices 9–10 as an irregular bright collection beneath the talar neck – sinus tarsi synovitis/ganglion vs. communicating subtalar effusion. Confidence: medium.\n\n**Bones / cartilage**\n- Small focal high‑signal focus in the central/medial talar dome (slice 8), subchondral, a few mm – small subchondral cyst or focal osteochondral lesion with marrow edema. Confidence: medium.\n- Dorsal talonavicular / naviculocuneiform region (slices 5–7): dorsal bright signal at the joint margins, consistent with dorsal capsulitis/marginal osteophytes with mild marrow/soft‑tissue edema. Confidence: medium‑low.\n- No fracture line, no diffuse marrow edema in tibia, calcaneus or fibula. Distal tibia and fibula otherwise normal.\n\n**Tendons**\n- Fluid within the flexor hallucis longus tendon sheath posterior to the talus and along the posteromedial calcaneus (slices 8–10), continuous with the posterior ankle recess – FHL tenosynovitis vs. communication with the effusion. Confidence: medium.\n- Fluid tracking along the medial flexor tendons (FDL/FHL) toward the plantar midfoot (slices 4–6, parallel bright lines) – medial flexor tenosynovitis. Confidence: low‑medium.\n- Peroneal tendons (slices 13–14): thin rim of fluid around the tendons posterior/inferior to the lateral malleolus with surrounding soft‑tissue edema – mild peroneal tenosynovitis. Confidence: medium.\n- Achilles tendon: normal thickness and low signal; small amount of fluid in the retrocalcaneal bursa region (slice 10). Confidence: low‑medium.\n- Tibialis posterior and extensor tendons appear intact.\n\n**Ligaments**\n- Anterior talofibular ligament not well assessed on sagittal STIR; periligamentous edema around the lateral malleolus (slices 13–15) is nonspecific but compatible with chronic lateral ligament injury. Confidence: low.\n- Plantar fascia: normal thickness and signal, no plantar fasciitis. Spring ligament region unremarkable.\n\n**Soft tissues**\n- Mild diffuse subcutaneous edema along the dorsum of the midfoot (slices 5–8) and around the lateral ankle (slices 13–15). Confidence: medium.\n- Heel fat pad normal.\n\n**Impression**\n1. Tibiotalar effusion with probable anterior synovitis/scar (post‑arthroscopy).\n2. Small talar dome subchondral lesion/cyst.\n3. Sinus tarsi and posterior subtalar fluid/synovitis.\n4. FHL and mild peroneal tenosynovitis.\n5. Dorsal talonavicular/midfoot capsulitis with mild edema.\nNo acute fracture, tendon tear or significant marrow edema identified on this sequence."
}