The diagnosis of villous synovitis should not be considered complete without _skiagraphy_ being undertaken to reveal or exclude osteophytic outgrowths. For the subjective symptoms and signs of _early_ osteoarthritis are practically identical with those of villous arthritis, and although the presence of osteoarthritic lesions elsewhere would be suggestive, skiagraphy alone will enable us to effect a differentiation with certainty. Indeed, Bassett Jones and myself are strongly of the opinion that the life history of osteoarthritis involves two stages: (1) a _primary_ or _pre-osteophytic_ phase, often of prolonged duration, whose clinical characteristics are those of villous hypertrophy; (2) a _secondary_ or _terminal_ stage, in which bony and cartilaginous outgrowths make their appearance. Other symmetrical disorders of the knees that may be wrongly ascribed to gout are hydrarthrosis and gummatous synovitis. _Bilateral Hydrarthrosis._—Given effusion into both knees which is _passive_, _copious_, and _persistent_ rather than recurrent, then its possible _infective_ origin must be carefully canvassed. The common sources are _gonorrhœa_, _syphilis_, and _tubercle_. The history or presence of an urethral discharge and detection of the gonococcus will identify the first named. In syphilis the existence of other lesions, the response to Wassermann’s test and specific treatment are the points on which to rely, and in tubercle, the detection of visceral foci and the sero-reaction will give the clue. As to the _intermittent_ type of hydrarthrosis, the remarkable _periodicity_ in incidence of the effusion will suffice to obviate any possibility of confusion. _Peri-synovial and Peri-bursal Gummata._—Affecting as they do commonly the knee joints of adults, these may, in the absence of a history of infection, be a source of error. The uneven and nodular swelling may quite easily be confounded with uratic deposits. Pain is slight and mobility but little impaired. The presence of neighbouring scars, a positive Wassermann reaction, and a favourable response to anti-syphilitic therapy will clear up the diagnosis. CHRONIC GOUT OF POLYARTICULAR DISTRIBUTION The clinical portrait of tophaceous gout when of widespread distribution is one of the most striking to be met with in the whole domain of medicine, but for the broad outlines of the picture presented we would refer the reader to the chapter dealing with the clinical description of chronic articular gout.