_Peri-articular tubercle and abscess_ may result from the spread of
disease from the bone or joint into the surrounding tissues, either
directly or by way of the lymphatics. A peri-articular abscess may
spread in several directions, sometimes invading tendon sheaths or
bursae, and finally reaching the skin surface by tortuous sinuses.
Reactive changes in the vicinity of tuberculous joints are of common
occurrence, and play a considerable part in the production of what is
clinically known as _white swelling_. New connective tissue forms in the
peri-articular fat and between muscles and tendons. It may be tough and
fibrous, or soft, vascular, and oedematous, and the peri-articular fat
becomes swollen and gelatinous, constituting a layer of considerable
thickness. The fat disappears and is replaced by a mucoid effusion
between the fibrous bundles of connective tissue. This is what was
formerly known as _gelatinous degeneration_ of the synovial membrane. In
the case of the wrist the newly formed connective tissue may fix the
tendons in their sheaths, interfering with the movements of the fingers.
In relation to the bones also there may be reactive changes, resulting
in the formation of spicules of new bone on the periosteal surfaces and
at the attachment of the capsular and other ligaments; these are only
met with where pyogenic infection has been superadded.
|