Quantitative evaluation of collagen volume in the infrapatellar fat pad. To measure the collagen volume, the sections with Mallory – Azan stain were projected onto a color imaging analysis system. In each section, 10 separate sites were analyzed and the collagen volume fraction was obtained by calculating the mean ratio of connective tissue to the total tissue area. The collagen volume ratio was increased in adrenomedullin (AM)-treated knees by 39% and 31% at 0.1 μg and 3 μg AM, respectively. Data expressed as the mean ± standard error of the mean. *P < 0.05, compared with contralateral knees.