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Table 1 Description of the Ankle Osteoarthritis Scoring System (AOSS)

From: Association between intraarticular cytokine levels and clinical parameters of osteochondritis dissecans in the ankle

Items Evaluation Explanation
Major criteria
1. Depth of cartilage damage Total points: 0–3 grade 0 (0 points): no grade 1 (1 point): <50% of total cartilage depth grade 2 (2 points): >50% grade 3 (3 points): full thickness cartilage defects The depth of cartilage loss was qualitatively rated in relation to the height of the adjacent intact cartilage or the expected, normal cartilage contour. In doubt, the sagittal T2-weighted sequence was used for the final decision.
2. Defect of the subchondral bone Total points: 0–3 grade 0 (0 points): no grade 1 (1 point): minimal (<2 mm) grade 2 (2 points): moderate (2-5 mm) grade 3 (3 points): severe (>5 mm) The depth of the osseous component of the osteochondral defect was scored by estimating the distance between the actual osteochondral defect and the extrapolated subchondral cortex mainly based on evaluation of the coronary or sagittal T1-weighted sequences.
3. Osteophytes Total points: 0–3 grade 0 (0 points): no grade 1 (1 point): minimal (<3 mm) grade 2 (2 points): moderate (3-5 mm) grade 3 (3 points): severe (>5 mm) Size was measured from the base to the tip of the osteophyte, baseline was defined as the natural course of the bone.
4. Subchondral cysts (largest diameter) Total points: 0–3 grade 0 (0 points): no grade 1 (1 point): minimal (<3 mm) grade 2 (2 points): moderate (3-5 mm) grade 3 (3 points): severe (>5 mm) Subchondral cysts were defined as structures of high signal intensity on T2-weighted images in the cancellous bone underlying the joint cartilage.
5. Bone marrow edema (largest diameter): Total points: 0–3 grade 0 (0 points) no, grade 1 (1 point): minimal (<5 mm) grade 2 (2 points): moderate (5-20 mm) grade 3 (3 points): severe (>20 mm) Bone marrow edema was assessed as an area of increased signal intensity on T2-weighted images in the subchondral cancellous bone.
Minor criteria
6. Anterolateral or anteromedial meniscoid Total points: 0–1 0 points: no 1 point: yes MR images were assessed for appearance of pathological anterolateral or anteromedial soft tissue structures.
7. Effusion Total points: 0–1 0 points: no 1 point: yes If more than a small, physiological sliver of synovial fluid was observed in the T2 images, joint effusion was assumed to be present.
8. Loose joint bodies Total points: 0–1 0 points: no 1 point: yes  
9. Synovitis Total points: 0–1 0 points: no 1 point: yes Synovitis was evaluated on sagittal images and was reflected by thickening and irregularity of the normally pencil-thin rim of high signal intensity synovium.
10. Soft tissue cysts (Baker cyst analog): Total points: 0–1 0 points: no 1 point: yes These structures may be considered as excrescences originating from the joint capsule. They are depicted as a circumscribed mass with intermediate signal intensity on proton density-weighted and high signal intensity on T2-weighted sequences and are usually observed in the triangle of calcaneus and Achilles tendon.
Summary Total points: 0-20