Nanocrystalline apatite-based biomaterials and stem cells are emerging research fields in orthopaedic surgery and traumatology that have the potential of improving quality of life of the elderly and enhance health-related socio-economic challenges. Nanocrystalline apatite-based biomaterials and especially calcium phosphate nano-biomaterials exploit new physical, chemical and biological properties that have the possibility to increase surface area and improve tissue integration. Stem cells of adult origin decrease inflammation, increase vascularity and are able to replace degenerated tissue cells during the process of regeneration. The bone is the only human tissue that regenerates. Musculoskeletal disorders including osteoporotic fractures and osteoarthritis decrease quality of life in the elderly and cause severe burden on economics. Nanocrystalline calcium phosphate bioceramics have the ability to prevent or treat osteoporotic fractures when combined with stem cells. These biomaterials may also be used for drug delivery purposes to treat bone infections when combined with stem cell as they can assist in treating osteoarthritis. Current research challenges are trying to overcome the toxicity and carcinogenesis with these cells and nanomaterials. Long-term stability of these cells and materials is another challenge for these materials. This chapter deals with nanocrystalline calcium phosphate bioceramics and mesenchymal stem cells.