They are not
peculiar to joints, for they are met with in tendon sheaths and bursae,
and their origin from synovial membrane may be accepted as proved. They
occur in tuberculosis, arthritis deformans, and in Charcot's disease,
and their presence is almost invariably associated with an effusion of
fluid into the joint. While they may result from the coagulation of
fibrin-forming elements in the exudate, their occurrence in tuberculous
hydrops would appear to be the result of coagulation necrosis, or of
fibrinous degeneration of the surface layer of the diseased synovial
membrane. However formed, their shape is the result of mechanical
influences, and especially of the movement of the joint.

_Clinically_, loose bodies composed of fibrin constitute an unimportant
addition to the features of the disease with which they are associated.
They never give rise to the classical symptoms associated with impaction
of a loose body between the articular surfaces. Their presence may be
recognised, especially in the knee, by the crepitating sensation
imparted to the fingers of the hand grasping the joint while it is
flexed and extended by the patient.

The _treatment_ is directed towards the disease underlying the hydrops.
If it is desired to empty the joint, this is best done by open
incision.

[Illustration: FIG. 166.--Radiogram of Multiple Loose Bodies in
Knee-joint and Semi-membranosus Bursa in a man aet. 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 th