CT arthrography (CTA) for evaluating cartilage defects would be beneficial in clinical practice. Since the contrast medium (CM) volume is often driven by operator experience, the aim was to evaluate the minimum volume of iodinated CM for CTA sufficient to identify iatrogenic cartilage defects in horse fetlock. The study was conducted on ex-vivo 32 distal limbs from adult horses collected at slaughter. Iatrogenic cartilage defects were arthroscopically made on fetlock, at 5 predetermined locations. Subsequently, CT scans were performed, according to the following protocol: precontrast scan, followed by subsequent scans with incremental volumes of CM, ranging from 2,5-40 ml (total of 10 scans per fetlock). Then, the cartilage defects were measured macroscopically using a calliper. CTA scans were evaluated by a single operator, and defects were assessed for presence/absence and volume measures. Data were expressed as median and interquartile values. The association between CT scan assessments and different CM volumes was examined with chi-square test. The correlation between CT scans and macroscopic assessments was evaluated using Spearman's coefficient. Significance was set at a p-value <
0.05. Twenty millilitres of CM were required to visualize 100 % of the defects, regardless of the location. A weak correlation was found between the defects' volume on macroscopic and CT scan assessment. Twenty millilitres of CM was sufficient to identify cartilage defects on the fetlock articular surface, supporting the conscious use of CM adequate for specific diagnostic purposes.