Objective To study the effects of abnormal mechanical load in developmental dysplasia of the hip (DDH) on the bone microstructure and blood vessels of the subchondral bone, and the correlation between the bone microstructure and blood vessels. Methods A newborn rat DDH model was constructed using the swaddling method, and histological staining such as hematoxylin-eosin staining, safranin-fast green staining, and immunohistochemical staining were performed on the articular cartilage and subchondral bone of the femoral head. The bone microstructure of the subchondral bone was analyzed by micro-computed tomography (Micro-CT). Results DDH rats showed degeneration of articular cartilage, accompanied by deterioration of the bone microstructure of the subchondral bone, decreased bone formation, and increased vascular formation. The level of vascular formation in the subchondral bone was positively correlated with the degree of deterioration of the bone microstructure. Conclusion Abnormal mechanical load in DDH leads to degeneration of articular cartilage, increased vascular formation in the subchondral bone, and deterioration of the bone microstructure of the subchondral bone. The correlation analysis reveals that abnormal vascular formation in the subchondral bone may be an important reason for the deterioration of the bone microstructure and the progression of DDH. This study provides a new research direction to explore the development of DDH.