Tendons transmit forces generated by muscle to move the joints they cross. Tendon problems are complicated by slow and incomplete healing as well as re-injury. Mesenchymal stem cell based therapies show promise in improving outcomes. Much of the work has been experimental, although early clinical use in equine strain-induced tendon injury supports the efficacy of this strategy. While much has been studied about the mechanisms of action of implanted MSCs, the relative importance of the various mechanisms is still unknown. Key areas of research that could prove pivotal in the clinical use of MSCs include the use of allogeneic cells, optimization of MSC culture, gene therapy, and mechanical stimulation techniques.