etween the psoas muscle and the capsule of the hip-joint_
may be the seat of tuberculous disease, and give rise to clinical
features not unlike those of disease of the hip-joint. The limb is
flexed, abducted and rotated out; there is a swelling in the upper part
of Scarpa's triangle, but the movements are not restricted in directions
which do not entail putting the ilio-psoas muscle on the stretch.

Cartilaginous and partly ossified loose bodies may accumulate in the
ilio-psoas bursa and distend it, both in a downward direction towards
the hip-joint, with which it communicates, and upwards, projecting
towards the abdomen.

The bursa beneath the quadriceps extensor--_subcrural bursa_--usually
communicates with the knee-joint and shares in its diseases. When shut
off from the joint it may suffer independently, and when distended with
fluid forms a horse-shoe swelling above the patella.

In front of the patella and its ligament is the _prepatellar bursa_,
which may have one, two, or three compartments, usually communicating
with one another. It is the seat of the affection known as "housemaid's
knee," which is very common and is sometimes bilateral, and, less
frequently, of tuberculous disease which usually originates in the
patella.

[Illustration: FIG. 116.--Great Enlargement of the Ischial Bursa.

(Mr. Scot-Skirving's case.)]

The bursa _between the ligamentum patellae and the tibia_ is rarely the
seat of disease. When it is, there is pain and tenderness referred to
the ligament, the patient is unable to extend the limb completely, the
tuberosity of the tibia is apparently enlarged, and there is a
fluctuating swelling on either side of the ligament, most marked in the
extended position of the limb.

Of the numerous bursae in the popliteal space, that _between the
semi-membranosus and the medial head of the gastrocnemius_ is most
frequently the seat of disease, which is usually of the nature of a
simple hydrops, forming a fluctuating egg-or sausage-shaped swelling at
the medial side of the popliteal space. It is flaccid in the flexed, and
tense in the extended position. As a rule it causes little
inconvenience, and may be left alone. Otherwise it should be dissected
out, and if, as is frequently the case, there is a communication with
the knee-joint, this should be closed with sutures.

[Illustration: FIG. 117.--Gouty Disease of Bursae in a tailor. The bursal
tumours were almost entirely composed of urate of sod