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 soda. (Cf.  Fig. 114.)]

An adventitious bursa may form over the lateral malleolus, especially in tailors, giving rise to the condition known as “tailor’s ankle” (Fig. 117).

The bursa between the tendo-calcaneus (Achillis) and the upper part of the calcaneus may become inflamed—­especially as a result of post-scarlatinal rheumatism or gonorrhoea.  The affection is known as Achillo-bursitis.  There is severe pain in the region of the insertion of the tendo-calcaneus, the movements at the ankle-joint are restricted, and the patient may be unable to walk.  There is a tender swelling on either side of the tendon.  When, in spite of palliative treatment, the affection persists or relapses, it is best to excise the bursa.  The tendo-calcaneus is detached from the calcaneus, the bursa dissected out, and the tendon replaced.  If there is a bony projection from the calcaneus, it should be shaved off with the chisel.

The bursa that is sometimes met with on the under aspect of the calcaneus—­the subcalcanean bursa—­when inflamed, gives rise to pain and tenderness in the sole of the foot.  This affection may be associated with a spinous projection from the bone, which is capable of being recognised in a skiagram.  The soft parts of the heel are turned forwards as a flap, the bursa is dissected out, and the projection of bone, if present, is removed.