Local Characters of Joint Swellings
These are best appreciated in the small joints of the hand. Osteoarthritis has an affinity for terminal joints—the so-called Heberden’s nodes. Another favourite site is the carpo-metacarpal joint of the thumb, while the preference of gout is for the metacarpo-phalangeal joint thereof and for the same articulation in the other digits.
The overlying skin, as a rule, is unchanged, and never assumes, as in gout, a dusky red or purplish hue. The margin of the articular surfaces, instead of being smooth and rounded, is broken and irregular, its nodular contour being due to osseous outgrowths studding the line of junction of the bones entering the articulation.[42]
In this respect they contrast with tophi, which are located near to, but not at, the level of the joint fissure. Again, unlike tophi, bony outgrowths are fixed, immutable, undergoing no change save in the direction of progressive enlargement. While the tendency of an osteoarthritic joint is to expand and increase, still the enlarged and gnarled joints never attain the colossal bulbous appearance presented by inveterate examples of tophaceous gout.