[The rheumatoid foot. Origin of deformations].

Deformations of the foot are a logical and predictable function of the biomechanics of the foot and the constraints undergone by the articulations of the foot, that are unstabilized by the inflammatory process. They result from the combination of three factors : anevolutive teno-articular synovitis, predictible forces (the weight of the extrinsic muscle, the anti-physiological foot), and the congenital morphotype of the foot. Typical deformations (peroneal " coup de vent " of the toes, triangular metatarsus), differ on the clinical level in keeping with the morphotype but respond to the same mechanism. The " coup de vent peronier " remains the most characteristic deformation and is furthered by the excentric action of the extrinsic muscles, and in particular the foot muscle. The common denomination of deformations of the back part of the foot is represented by the valgus calcanean, linked to the action of the weight on the orsion forces that is more or less modified. A better knowledge of the cause of these deformations would make it possible to avoid, if not their apparition, at least their worsening.