Fig. 166.—Radiogram of Multiple Loose Bodies in Knee-joint and Semi-membranosus Bursa in a man æt. 38.
(Mr. J. W. Dowden's case.)
Bodies composed of Organised Connective Tissue.—These are comparatively common in joints that are already the seat of some chronic disease, such as arthritis deformans, Charcot's arthropathy, or synovial tuberculosis. They take origin almost exclusively from an erratic overgrowth of the fringes of the synovial membrane, and may consist entirely of fat, the arborescent lipoma ([Fig. 159]) being the most pronounced example of this variety. Fibrous tissue or cartilage may form in one or more of the fatty fringes and give rise to hard nodular masses, which may attain a considerable size, and in course of time may undergo ossification.
Like other hypertrophies on a free surface, they tend to become pedunculated, and so acquire a limited range of movement. The pedicle may give way and the body become free. In this condition it may wander about the joint, or lie snugly in one of its recesses until disturbed by some sudden movement. A loose body free in a joint is capable of growth, deriving the necessary nutriment from the surrounding fluid. The size and number of the bodies vary widely. Single specimens have been known to attain the size of the patella. The smaller varieties may number considerably over a hundred.
a b
Fig. 167.—Loose Body from Knee-joint of man æt. 25. Natural size.
a = Convex surface. b = Concave surface.