['To investigate the effects of Huogu I formula on regulation of lipid metabolism in steroid-induced osteonecrosis of the femoral head (SONFH) rats and verify our hypothesis that Huogu I formula regulates lipid metabolism by down-regulating peroxisome proliferator-activated receptor gamma (PPARgamma) expression and activating Wnt signaling pathways.', 'Eighty-five rats were divided into four groups: control, model, Huogu 15 g/kg and Huogu 30 g/kg. Six weeks later, animals were anaesthetized, femora was dissected for histopathological examination of the osteonecrotic changes and repair processes, micro computed tomography (Micro-CT)-based micro-angiography was performed to assess vascularization. Serum lipid levels were detected by haematological examination. The expressions of PPARy, Wnt3a, low density lipoprotein receptor-related protein 5 (LRP5) and beta-catenin were evaluated by immunohistochemistry, Western blot and quantitative real-time polymerase chain reaction analyses.', 'The incidence of osteonecrosis, ratio of empty lacuna, adipose tissue area and adipocyte perimeter in the bone marrow were dramatically lower in the Huogu I formula treatment groups. By micro-CT quantification, Huogu I formula treatment dose-dependently increased vessel volume, vessel surface, percentage of vessel volume and vessel thickness of the femoral heads of SONFH rats. Levels of serum lipid in Huogu 15 g/kg and Huogu 30 g/kg groups reduced significantly. Huogu I formula treatment could suppress the expression of PPARy and increase the expressions of Wnt3a, LRP5 and beta-catenin at both protein and mRNA levels.'] Does huogu I formula prevent steroid-induced osteonecrosis in rats by down-regulating PPARgamma expression and activating wnt/LRP5/ beta-catenin signaling?