There is a growing need for noninvasive and inexpensive methods that can effectively be used on a large scale, to detect an onset of early osteoarthritis in human knee joints. Of many possible options, fractal analysis of two-dimensional projection x-ray images of trabecular bone (TB) texture. appears as one of the best approaches. However, there are some problem.,, associated with the characterization of the roughness and anisotropy of the bone texture. To resolve these prohlems, a modified Hurst orientation transform (HOT) method, previously developed by the authors, has been used in this study. The advantages of the HOT method over other techniques used to analyze bone texture. are that it calculates a two-dimensional fractal dimension in all possible directions and also provided a measure of anisotropy for both surfaces exhibiting strong anisotropy and surfaces exhibiting weak anisotropy. In this study. the accuracy of the HOT method in measuring the bone texture roughness and anisotropy, together with the effects of image noise, blur, exposure, magnification, and projection angle on its performance were investigated. Computer-generated images of fractal surfaces and x-ray images obtained for a human tibia head were used, Results obtained show that the HOT method can effectively be used to characterize the roughness and anisotropy (isotropy) of TB texture. (C) 2002 American Association of Physicists in Medicine.