Disordered networks of fragile elastic elements have been proposed as a model of inner porous regions of large bones [Gunaratne et.al., http://xyz.lanl.gov]. It is shown that the ratio Γ of responses of such a network to static and periodic strain can be used to estimate its ultimate (or breaking) stress. Since bone fracture in older adults results from the weakening of porous bone, we discuss the possibility of using Γ as a non-invasive diagnostic of osteoporotic bone.Osteoporosis is a major socio-economic problem in an aging population [1]. Unfortunately, therapeutic agents which can prevent and even reverse osteoporosis often induce adverse side effects [2]. Thus, non-invasive diagnostic tools to determine the necessity of therapeutic intervention are essential for effective management of osteoporosis. Bone Mineral Density (BMD), or the effective bone density is the principal such investigative tool [3]. Ultrasound transmission through bone [4] and geometrical characteristics of the inner porous region or trabecular architecture (TA) [5][6][7] are being studied as complementary diagnostics.In older adults, weakening of the TA is the principal cause of increased propensity for bone fracture [4]. Analysis of models can complement mechanical studies of bone in aiding the identification of precursors of the weakening of a TA. In Ref. [8], it was proposed that a system to model mechanical properties of a TA can be obtained by adapting a disordered network of fragile elastic elements [9]. The model system includes potential energy contributions from elasticity and from changes in bond angles between adjacent springs. Furthermore, springs that are strained beyond (a predetermined value) ǫ and bond angles that change more than δ are assumed to fracture and are removed from the network. The inertia of the network is modeled by placing masses at the vertices. When in motion, each mass experiences a dissipative force proportional to its speed. Osteoporosis is modeled by random removal of a fraction ν of springs from the network, and the bone density is estimated by the fraction of remaining links. Therapeutic regeneration is introduced by strengthening springs that experience large strain (as suggested by Wolff's law [10]).Numerical studies of the system show analogs of several mechanical properties of bone including, (1) an initially linear stress vs. strain curve that becomes nonlinear beyond the fracture of elastic elements, (2) an exponential reduction of the ultimate (or breaking) stress with decreasing BMD, and (3) a dramatic increase of bone strength following therapeutic regeneration [8]. Together they support the conjecture that elastic networks are a suitable model of mechanical properties of bone. In this Letter we use results from a numerical study of the model to introduce a possible diagnostic tool for osteoporosis. FIG. 1. The stress distributions on networks of size 60 × 60 with (a) ν = 10%, and (b) ν = 30% representing "healthy" and "osteoporotic" bone respectively. For clarity only the compressed bonds...