ObjectiveTo introduce a technique of frozen sections for undecalcified bone and discuss its feasibility by observing the fluorescence distribution of the bone and cartilage. MethodsThe male Sprague Dawley transgenic rats at the age of 8 weeks, which express green fluorescent protein were selected to isolate the whole knee sectioned by the undecalcified bone frozen section technique. Under the fluorescence and light microscopy, the fluorescence and structure were observed within the organization of slice. Immunohistochemical staining (collagen type Ⅰ and Ⅱ), HE staining, toluidine blue staining, and Alizarin red staining were performed to observe the distribution of fluorescent substance and cartilage and bone structure. ResultsThe thickness of sections prepared by this technology was 6 μm. General observation showed that the structure of sectioned joint was complete. Under the light microscope, the morphology of cartilage cells, the arrangement of subchondral bone, and trabecular bone traveling could be clearly distinguished. Under fluorescence microscope, green fluorescence was shown in the joint soft tissue, cartilage tissue, and bone tissue; collagen type Ⅰ expressed in the bone tissue, collagen type Ⅱ in cartilage tissue. HE staining and toluidine blue staining could clearly distinguish the morphology of the cartilage layer. Alizarin red staining showed the structural integrity of subchondral bone plate and the organization within the meniscus, and proximal tibia cortical bone continuity. ConclusionThe fluorescence distribution can be directly observe in the bone and cartilage by sectioning of frozen undecalcified bone. This new technology can shorten the cycle of preparing sections.