The frequency of small joint effusions in the population of Sudbury, Massachusetts, as determined by the clinical maneuver called the "bulge sign", was estimated to be 16%. The prevalence rate was found to be higher in males than in females, but the increase with advancing years was prominent in women only. While clinically demonstrable fluid in the kneejoint was more common in persons with other signs of joint disease, these individuals formed a small proportion of the total population with demonstrable knee effusions. It is concluded that the sign also identifies a hitherto unrecognized upper range of normal for knee-joint fluid, and it is tentatively proposed that physique may be a factor related to knee-joint fluid volume.
Effusions in the knee joint may be detected by a number of methods including palpation, ballottment of the patella and the "bulge sign". Although the latter maneuver may not be as well known or as widely used as the other two procedures, it has the presumed advantage of being less dependent on subjective interpretation since it relies on the demonstration of a visible fluid wave over an affected joint. Recently, the "bulge sign" was evaluated in a random sample of the town of Sudbury, Massachusetts; which is the site of a long term