reatment._--The limb is immobilised on a posterior splint so padded
as to allow slight flexion at the knee, and extension applied with
sufficient weight to relieve the pain; it is also of benefit to induce
hyperaemia by one or other of the methods devised by Bier. To tap the
joint, the needle is introduced obliquely into the supra-patellar
pouch, and if it is necessary to open the joint, the incision is made
on one or on both sides of the patella, and Murphy's plan of inserting
formalin-glycerine may be employed. If the infection progresses and
threatens the life of the patient, it may be necessary to lay the
joint freely open from side to side, sawing across the patella, and,
the limb being flexed, the whole wound is left open and packed with
gauze. As the infection subsides, the limb is gradually straightened.
If these methods fail, amputation through the thigh may be the only
means of saving life.

#Arthritis deformans# affects the knee more frequently than any of the
other large joints. The changes related to the synovial membrane here
attain their maximum development, and may assume the form of hydrops
with or without fibrinous bodies, or of overgrowth of the synovial
fringes and the formation of pedunculated loose bodies. It is
suggested that these synovial changes follow upon repeated sprains or
upon a previous pyogenic infection of the joint. The effusion and
stretching of the ligaments that follow upon a sprain are incompletely
recovered from; the synovial membrane becomes puckered, the quadriceps
atrophies and no longer puts the ligamentum mucosum on the stretch;
and the infra-patellar pad of fat, not undergoing the normal
compression during extension, is readily nipped between the femur and
tibia. Each nipping implies a fresh sprain, with return of the
effusion, and so a vicious circle is set up which terminates in what
has been called a _villous arthritis_, with fringes and loose bodies;
in time, the articular cartilage at the line of the synovial
reflection undergoes fibrillation and conversion into connective
tissue, and the process spreading to the articular surfaces, the
picture of a rheumatoid arthritis is complete. Fibrillation of the
cartilage imparts a feeling of roughness when the joint is grasped
during flexion and extension, and lipping of the margins of the
trochlear surface of the femur may be felt when the joint is flexed;
it is also readily seen in skiagrams. When a portion of the "lipping"
i