High magnification of the anterior edge of the tibial plateau in the HFD and the control diet mice at the indicated weeks after diet initiation.

Representative HE stained sections (a–f) from control mice (a–c) and mice fed the HFD diet (d–f). g, h, i are neighbor sections in Safranin-O staining of d, e, f respectively. Increased synovial cell aggregation was observed at the anterior edge of the tibial plateau and synovium in the HFD (asterisk) mice beginning at week eight. Simultaneously, angiogenesis was activated within the IPFP (arrows) in the HFD group. Osteophytes were first noted at week eight of the HFD (triangles).