**MRI RIGHT ANKLE**

**CLINICAL INDICATION:** Male in his 30s with chronic right ankle pain and a remote history of an ankle sprain.

**FINDINGS:**

**Bones and Cartilage:**
*   **Osteochondral Lesion:** There is a focal osteochondral lesion (OCL) of the talar dome (with observations noting involvement of the anterior and medial aspects). This is characterized by subchondral cystic change, a focal defect/irregularity of the overlying articular cartilage, and surrounding reactive bone marrow edema. 
*   **Anterior Impingement:** Prominent "kissing" osteophytes are present at the anterior margin of the distal tibial plafond and the opposing dorsal aspect of the talar neck. 
*   **Lateral Malleolus:** There is a well-corticated bony fragment located just inferior to the tip of the lateral malleolus, consistent with an old, ununited avulsion fracture (os subfibulare). There is no associated acute bone marrow edema.
*   **Other Osseous Structures:** A prominent posterior talar process (Stieda process) is noted. Mild dorsal osteophyte formation (beaking) is seen at the talonavicular joint. The regional bone marrow signal is otherwise normal and fatty.

**Ligaments and Soft Tissues:**
*   **Lateral Collateral Ligament Complex:** The anterior talofibular ligament (ATFL) and calcaneofibular ligament (CFL) are markedly thickened, irregular, and demonstrate heterogeneous intermediate-to-low signal intensity, lacking their normal thin, taut appearance. 
*   **Anterolateral Gutter:** There is ill-defined soft tissue thickening and loss of normal bright fat signal in the anterolateral gutter, adjacent to the ATFL/CFL origins and the os subfibulare.
*   **Sinus Tarsi:** The normal fat within the sinus tarsi is partially obliterated and replaced by heterogeneous, hyperintense fluid signal, consistent with chronic scarring and inflammation.
*   **Medial and Syndesmotic Ligaments:** The medial deltoid ligament complex, posterior talofibular ligament (PTFL), and the distal tibiofibular syndesmotic ligaments appear intact and unremarkable.

**Tendons:**
*   The Achilles tendon and plantar fascia demonstrate normal thickness, contour, and signal intensity at their calcaneal insertions.
*   The medial (posterior tibial, flexor digitorum longus, flexor hallucis longus), lateral (peroneal brevis and longus), and anterior (extensor) tendons are intact with normal caliber and signal intensity. No evidence of high-grade tearing or significant tenosynovitis.

**Joints and Fluid:**
*   There is a moderate tibiotalar joint effusion extending into the anterior and posterior recesses.
*   Intermediate-signal soft tissue thickening is present in the anterior tibiotalar joint recess adjacent to the impinging osteophytes, representing reactive synovitis/capsular thickening.

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**IMPRESSION:**

1. **Chronic Lateral Ankle Injury and Anterolateral Impingement:** Markedly thickened and irregular ATFL and CFL consistent with chronic tearing and scarring from the remote ankle sprain. This is associated with an old, ununited avulsion fracture at the lateral malleolar tip (os subfibulare) and adjacent soft tissue thickening in the anterolateral gutter, highly suggestive of anterolateral impingement syndrome. *(Confidence: High)*
2. **Active Osteochondral Lesion:** Focal osteochondral lesion of the talar dome demonstrating subchondral cystic change, overlying cartilage irregularity, and surrounding reactive bone marrow edema. *(Confidence: High)*
3. **Anterior Bony Impingement:** Prominent "kissing" osteophytes at the anterior tibial plafond and dorsal talar neck with adjacent reactive synovitis/capsular thickening in the anterior joint recess. *(Confidence: High)*
4. **Sinus Tarsi Syndrome:** Signal alteration and partial obliteration of the sinus tarsi fat, consistent with chronic scarring/inflammation of the interosseous ligaments. *(Confidence: Medium to High)*
5. **Joint Effusion:** Moderate tibiotalar joint effusion. *(Confidence: High)*