The renewal of living bone is continuous and influenced by many mechanical and biological factors. A reliable prediction of such phenomena should include many external sources such as mechanical, biological, electrical, neurological, and others, triggered by genetic and/or epigenetic factors. In the current work, we consider as external sources, (i) the mechanical energy developed by the applied mechanical load and sustained by the bone cells, (ii) the concentration of nutriments (oxygen and glucose) available for cell survival, and (iii) cell activity triggered by the nutriments available and the mechanical force applied. We study the bone cell interactions, and more specifically the competition between osteoblasts and osteoclasts leading the bone density kinetics over time, in order to try to predict the evolution of osteoporosis with age. Three-dimensional finite element models are developed to calculate the model variable evolutions for different bone microstructures as a function of applied mechanical load corresponding to standard body weight. The bone density evolution is then calculated and compared with literature data and show good correlation for the studied samples. This could help in the understanding and prediction of osteoporotic degradation mechanisms for better medical prevention.