First I should state I'm not in ortho, but have worked some on tissue engineering. The use of allogenic stem cells (cells from another person) brings a lot of practical concerns, particularly in the need for HLA matching, but is the direction of a lot of interesting research.
As may have noticed in the review you cited, much of the work on joint repair focuses on delivering the patient's own stem cells in a "patch" directly to the injury site. The main concerns in doing so are that the actual injury site gets repaired (as apposed to a ubiquitous smaller tissue growth) and that teratoma formations or other erroneous and harmful growths don't occur.
On the other hand, the advantage of just being able to inject cells (+factors) would be the simplicity of the procedure. It has been done in one case patient and in rats, but the more common procedure is to use bone marrow cell concentrate (BMCC).
BMCC's do not have the concentrations of stem cells that cultures specifically sorted/selected then expanded do. It is still exceedingly costly and difficult to culture a patient's mesenchymal stem cells (MSC's). You look at MSC's wrong and they differentiate. It is however, to the point where it can be reliably done.
So why use bone marrow concentrate instead? It can be produced much faster and with equipment/techniques most hospitals already have on hand. And if we're going to move to an injection over surgical placement of a patch, then we have to make it significantly easier to justify not treating the damage directly.
