Background: Adult mesenchymal stem cells (MSCs) were first isolated from bone marrow by Friedenstein in 1976. These cells were clonogenic, non-haematopoietic, and able to replicate extensively in vitro. The fields of regenerative medicine and tissue engineering have grown dramatically since their inception. In the decades since, MSCs have been identified from mesoderm-, endoderm- and ectoderm-derived tissues. In light of our ageing population, the need for effective cell-based therapies for tissue repair and regeneration is ever-expanding. Objectives: The purpose of this systematic review was to summarise evidence from the most recent studies outlining different sources of adult MSCs and their suitability in musculoskeletal applications. Methods: Online published articles were searched for using the PubMed/MEDLINE and Ovid databases, and relevant articles fulfilling the pre-defined eligibility criteria were analysed. Results: To date, MSCs have been isolated from a number of adult tissues, including trabecular bone, adipose tissue, bone marrow, synovium, dermis, periodontal ligament, dental pulp, bursa and the umbilical cord. Bone marrow MSCs are currently considered the gold standard, with which newly discovered sources are compared on the basis of their renewal capabilities and multipotency. Furthermore, MSCs have been successful in the regeneration of osteonecrosis, osteoarthritis, bony defects, fracture remodeling and so on. Conclusion: Unfortunately, significant hurdles remain and will need to be overcome before tissue engineering using MSCs becomes routine in clinical practice. Thus, further research and understanding are required into the safe and effective sourcing and application of mesenchymal stem cells in musculoskeletal applications.