The complex lesions of joints observed in the course of posterior spinal sclerosis, the spinal arthropathies of Charcot, probably belong to this category. The affected joint (knee, shoulder, or ankle) rather suddenly swells, and the swelling usually invades the rest of the member or extends to the next distal joint; it is a hard, semi-elastic swelling unlike common œdema. After its gradual subsidence it is found that changes have taken place in the articulation itself, and later distinct evidences of destructive disease, such as erosion of cartilages, relaxation of ligaments, swelling, are observed. In many cases extra-articular lesions appear in the shape of osteophitic formations from the adjacent bones. The hydrarthrosis may persist or disappear. So complete may be the destruction of {57} the joint that—for example, in a case of arthropathy of the knee—the leg may be twisted about in all directions, and even over-extended so as to lie upon the anterior surface of the thigh. Examination of the joint post-mortem reveals non-suppurative destruction of all its component parts, cartilages, ligaments, and epiphyses; the eroded, deformed ends of the bones rub against one another in a false joint-cavity formed of the skin, connective tissue, tendons, and remains of ligaments. The absence of pain and tenderness in the course of arthropathies is a striking feature—so much so that when, in an adult patient, it is observed that manipulation or puncture of a diseased joint is painless, special inquiry should be made for symptoms of posterior spinal sclerosis.[7] [Footnote 7: We have known one case in which the diagnosis of tabes dorsalis was made (and verified after death) in this way, after the surgeon in charge of the patient had mentioned the fact that puncturing a swollen diseased knee-joint was painless.]