Objective To study the effects of an abnormal mechanical load in the developmental dysplasia of the hip (DDH) on the bone microstructure and blood vessels of the subchondral bone, and the correlation between bone microstructure and blood vessels. Methods A newborn rat DDH model was constructed using the swaddling method. Histological staining such as hematoxylin-eosin staining, safranin-fast green staining, and immunohistochemical staining was performed on the articular cartilage and subchondral bone of the femoral head. The microstructure of the subchondral bone was analyzed using microcomputed tomography (micro-CT). Results The DDH rats showed degeneration of the articular cartilage accompanied by deterioration of the 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. Conclusions An abnormal mechanical load in the DDH causes articular cartilage degeneration, increased vascular formation in the subchondral bone, and subchondral bone microstructure deterioration. A correlation analysis revealed that the abnormal vascular formation in the subchondral bone may be an important factor causing the deterioration of bone microstructure and progression of DDH. This study has provided a new direction for the development of DDH.