I came across this post on The Node with some fantastic imaging from Zelzer and colleagues at the Weizmann of the cells that connect tendon to bone.  The paper sheds light on the developmental origins of the cells that form the eminences; the units that connect tendon to bone. As it turns out, these do not originate from cartilage (chondrocytes), as previously thought, but instead from a separate lineage specified slightly later in development.  These progenitor cells can be identified by the genes they express.  In the image below, the arrows point to these cells, represented in green [Sox9-positive (green), Col2a1-negative (red)].

Blitz et al. 2013 Development 10.1242/dev.093906