Entheseal endochondral bone formation in male DBA/1 paws. (A) H&E staining of a DBA/1 hind paw showing new cartilage and bone formation which originates from the enthesis. In (B), Toluidine blue staining of chondrogenic differentiation which occurs on both the proximal and distal side of the joint, resulting in ankylosis and loss of function of the joint. A’ and B’ showing higher magnifications of boxed areas in A and B, respectively. Scale bars: 500 μm in A and B, 125 μm in A’ and B’.