Cartilage tissue consists of chondrocytes and cartilage matrix, cartilage tissue and its surrounding cartilage membrane constitute cartilage, cartilage is classified into hyaline cartilage, elastic cartilage, and fibrous cartilage according to the cellulose content contained in the matrix, and there are various methods of cartilage staining, such as Toluidine Blue, Alisin Blue, and Saffron O method.

Cartilage staining solution (saffron O method) staining principle lies in the alkalophilic cartilage and alkaline dye saffron O combined with red, saffron O is a cationic dye combined with multiple anions, which shows that cartilage is based on the combination of cationic dyes and anionic groups in polysaccharides (chondroitin sulfate or keratan sulfate), saffron O coloring and the concentration of anions approximately proportional to the relationship between the content of indirectly reflecting the content and distribution of proteoglycans in the matrix; when cartilage is damaged, it is divided into transparent cartilage, elastic bone, and fibrous bone. When the cartilage is damaged, the glycoproteins in the cartilage will be released, so that the distribution of matrix components is not uniform, which leads to the light staining or non-staining of Saffron O. The image analysis software can be used to quantitatively analyze the Saffron O-stained cartilage matrix, and the Saffron O differentiation is very critical, and the over-differentiation is easy to lead to the section not staining, and the under-differentiation is easy to lead to the section staining is too dark.