* A syndrome of acute onset of inflammation over interphalangeal joints heralding deforming osteoarthritis may be intermediate between degenerative and rheumatoid joint diseases. The syndrome appears predominantly in women of menopausal age and is remarkably symmetrical. In a prospective study of 170 propositi, later changes more characteristic of rheumatoid arthritis than of generalized or erosive osteoarthritis developed in 15.3%. (JAMA 232:157-159, 1975) ********** VARIOUS recent observations of changes at the molecular, cellular, or tissue level delineate the process that ultimately leads to osteoarthritis. The chemical and physical alterations reflect repeated trauma of any degree, developmental factors, the action of proteolytic enzymes and superoxide radical (1) elaborated during inflammation from any cause, and the gamut of factors contributing to aging. While the late elaboration of growth hormones in acromegaly is clearly related to proliferative and degenerative changes at joints, the possible influence of other hormonal imbalances has only been inferred. Thus, the development of nodose deformities resulting from narrowing of joints and proliferative bone changes at their margins in women during the years surrounding menopause implies at least a contributory role for endocrine changes. In addition, a family history of osteoarthritis is often obtainable, in which women are much more at risk, and at earlier ages, than men. While there may be common basic mechanisms underlying the development of so-called degenerative changes of joints, the modes of expression readily segregate into various clinical syndromes. The majority of instances are provoked by exogenous or developmental stimuli, which afflict single joints or an anatomically related sequence of joints. The fact that the more generalized variety, (2-5) chiefly interphalangeal but with associated large-joint and spinal lesions, develops in close temporal relationship at a number of different sites suggests a response to exogenous stimuli. In most cases, the onset is insidious, and pain is minimal to absent, becoming noticeable only after trauma to a somewhat deranged joint. (6) In some instances, however, the onset is heralded by inflammation. (7) In the surrounding skin, the classic signs become apparent: redness, warmth, swelling, pain and tenderness, and dysfunction. According to Waxman and Sledge, (8) the qualification that the inflammation afflicts the surrounding tissues is unnecessary, as they have accumulated biochemical data to prove inflammatory changes within the joints as well. Levels of lysosomal proteolytic enzymes in knee joints that are developing erosive osteoarthritis are intermediate between normal and those levels found in standard degenerative joint disease and rheumatoid arthritis. The term, "inflammatory osteoarthritis," thus serves as a label for those of generalized osteoarthritis that begin abruptly, have inflammatory components, and subside, with sequalae that constitute the classic changes of osteoarthritis. These are generally erosive, as in the syndrome described by Peter and co-workers, [Text unreadable in original source.] but nonerosive and even ankylosing interphalangeal osteoarthritis may also result. (7) Interphalangeal Osteoarthritis A correlative analysis of 170 patients (164 women, six men) who, during a five-year period, were first seen with acute onset of interphalangeal osteoarthritis suggests that the syndrome is remarkably symmetrical. (7) Each distal interphalangeal joint was involved in more than 70% of patients, as shown in Table 1. Each proximal interphalangeal joint was involved in approximately 50%. The interphalangeal and metacarpophalangeal joints of the thumb and the trapeziometacarpal joint were frequent sites of predilection, but, to a lesser extent, all metacarpophalangeal joints could participate in the syndrome. Significantly, the joints of the ulnar side of the wrist and carpus were universally spared. …