The elusive concept of bone quality.

This paper outlines information from recent publications that aid our understanding of bone quality in relation to osteoporosis. In practical terms, bone quality designates the properties of bone that contribute to strength but are not assessed by bone densitometry. While osteoporosis is still defined in terms of bone density, the limitations of this approach, long questioned, have become indisputable. In parallel, the results of treatment trials of antiresorptive agents demonstrate that bone density is a flawed surrogate for bone fragility and a weak indicator of antifracture efficacy. The case for emphasizing bone turnover in assessing fracture risk, has become increasingly strong, and a redefinition of osteoporosis on this basis may well occur. New technologies for studying bone microstructure and matrix composition, merging with sophisticated biomechanical assessments, are advancing our ideas regarding bone "damageability" and its effects over time.