[Chronic disease of the two sesamoid bones of the lower foot of the horse].

The aetiology and pathogenesis of navicular bone disease and sesamoidosis are discussed on the basis of findings reported in the literature and research. A marked similarity is found to be present between the clinical presentation, aetiology and pathogenesis of these two diseases. In addition, the intra and juxta-articular signs of degeneration as seen in these diseases are similar to those seen in various forms of arthrosis. Circulatory disturbances resulting from partial or complete arterial occlusion, caused by arteriosclerosis, are likely to play an important role in the cause of degeneration of various anatomical structures occurring in navicular bone disease and sesamoidosis. In contrast, it is unlikely that overloading is a major factor in the aetiology of navicular bone disease and sesamoidosis, although it may be of importance in its pathogenesis. For a full understanding of the cause of arteriosclerosis, far more fundamental research is required.