The present paper presents the concepts of the biomechanical theory, which has gained considerable significance in current German legislation on occupational diseases (Berufskrankheiten) because of its use, together with occupational epidemiological methods, to establish statistical relationships with causality of degenerative arthrosis. Whether epidemiological evidence can demonstrate causal associations is discussed critically in the light of generally accepted criteria of causality. Introduced is a biologically based theory of degenerative arthrosis which focusses on organspecific capillary degeneration affecting the musculosceletal system. Metabolic syndrome is a culmination of such capillary-damaging processes (diabetes mellitus, hypertension, disturbances in fat metabolism, adipositas) with significant multi-organ comorbidity. The “lower class syndrome“ is introduced and defined as a sociological and medical entity with complex interrelations of social status, psychosocial factors, class-specific attitudes, metabolic disturbances and arteriosclerotic multi-organ degeneration. The common biological basis of metabolic syndrome and lower class syndrome — macroarteriosclerosis and microarteriosclerosis — is discussed with reference to its socio-political impact. Epidemiological interpretation of the association of physical strain at work and the development of degenerative osteoarthritis is brought back to its biological basis, and the usefulness of the biomechanical theory in this context is discussed critically.
