-"weaver's" or
"tailor's bottom" (Fig. 116). These affections are characterised by an
effusion of fluid into the sac of the bursa with thickening of its
lining membrane. While friction and pressure are the most evident
factors in their production, it is probable that there is also some
toxic agent concerned, otherwise these affections would be much more
common than they are. Of the countless housemaids in whom the
prepatellar bursa is subjected to friction and pressure, only a small
proportion become the subjects of housemaid's knee.

_Clinical Features._--As these are best illustrated in the different
varieties of prepatellar bursitis, it is convenient to take this as the
type. In a number of cases the inflammation is acute and the patient is
unable to use the limb; the part is hot, swollen, and tender, and
fluctuation can be detected in the bursa. In the majority the condition
is chronic, and the chief feature is the gradual accumulation of fluid
constituting the _bursal hydrops_ or _hygroma_. When the affection has
lasted some time, or has frequently relapsed, the wall of the bursa
becomes thickened by fibrous tissue, which may be deposited irregularly,
so that septa, bands, or fringes are formed, not unlike those met with
in arthritis deformans. These fringes may be detached and form loose
bodies like those met with in joints; less frequently there are
fibrinous bodies of the melon-seed type, sometimes moulded into circular
discs like wafers. The presence of irregular thickenings of the wall, or
of loose bodies, may be recognised on palpation, especially in
superficial bursae, if the sac is not tensely filled with fluid. The
thickening of the wall may take place in a uniform and concentric
fashion, resulting in the formation of a fibrous tumour--_the solid
bursal tumour_--a small cavity remaining in the centre which serves to
distinguish it from a new growth or neoplasm.

[Illustration: FIG. 113.--Hydrops of Prepatellar Bursa in a housemaid.]

The _treatment_ varies according to the variety and stage of the
affection. In recent cases the symptoms subside under rest and the
application of fomentations. Hydrops may be got rid of by blistering,
by tapping, or by incision and drainage. When the wall is thickened, the
most satisfactory treatment is to excise the bursa; the overlying skin
being reflected in the shape of a horse-shoe flap or being removed along
with the bursa.

#Other Diseases of Bursae# are associated