Literature data concerning the biology and differentiation potential of mesenchymal stem cells (MSCs) have become huge in less than 10 years, although some of these data still remain contradictory. MSCs seem to be a very promising tool for cell therapy because of their peculiar characteristics, which mimic partially those of embryonic stem cells, but with some advantages in terms of availability, expandability, transplantability, and ethical implications. We discuss here the potential use of MSCs in degenerative or inflammatory diseases involving bone, cartilage, tendon and muscle tissues, on the basis of the experimental evidence.