Bone mineral density and joint cartilage: four clinical settings of a complex relationship in osteoarthritis.

Experimental and clinical data support the hypothesis that both high and low bone mineral density (BMD) conditions, including osteoporosis, may induce osteoarthritis. However, these conditions do not always predispose to osteoarthritis progression. Four clinical settings could arise from this relationship, and furthermore two phenotypes may be identified whether early osteoarthritis coexists with high or low BMD.