Study objective: to identify homogeneous, distinct subgroups of osteoarthritis patients based on distribution of osteoarthritis lesions.
Study design: cross-sectional, prospective, multicenter. Patients with osteoarthritis of the hip, knee, fingers, or spine.
Data collected: clinical and radiologic features at 41 joint sites.
Methods: multivariate statistical analysis including a) k-mean clustering analysis followed by ascending hierarchical classification b) and a tree-structured discriminant method to confirm and to characterize the subgroups obtained using the clustering method.
Results: The 1021 patients were first classified into five categories with an error rate (obtained by cross-validation) of 7.6%. The tree obtained by segmentation took into account manifestations of osteoarthritis at the hands, knees and spine. Irrespective of the reason for seeking medical advice, patients with bilateral involvement of the fingers or with involvement of the spine and both femorotibial joints were classified as having generalized osteoarthritis; in contrast, focal osteoarthritis was defined as the absence of involvement of the fingers and of either the spine or the knees.
Conclusion: The statistical analysis provided a classification system that would be easy to use in everyday clinical practice. Prospective studies are needed to evaluate the potential clinical relevance of this system.