rmation of a false joint.

When bony ankylosis has occurred with the joint in an undesirable
attitude--for example flexion at the hip or knee--it can sometimes be
remedied by osteotomy or by a wedge-shaped resection of the bone, with
or without such additional division of the contracted soft parts as will
permit of the limb being placed in the attitude desired.

Bony ankylosis of the joints of a finger, whether the result of injury
or disease, is difficult to remedy by any operative procedure, for while
it is possible to restore mobility, the new joint is apt to be
flail-like.

_Locking._--A joint is said to lock when its movements are abruptly
arrested by the coming together of bony outgrowths around the joint. It
is best illustrated in arthritis deformans of the hip in which new bone
formed round the rim of the acetabulum mechanically arrests the
excursions of the head of the femur. The new bone, which limits the
movements, is readily demonstrated in skiagrams; it may be removed by
operative means. Locking of joints is more often met with as a result of
injuries, especially in fractures occurring in the region of the elbow.
In certain injuries of the semilunar menisci of the knee, also, the
joint is liable to a variety of locking, which differs, however, in many
respects from that described above.

#Errors of Development.#--These include congenital dislocations and
other deformities of intra-uterine origin, such as abnormal laxity of
joints, absence, displacement, or defective growth of one or other of
the essential constituents of a joint. The more important of these are
described along with the surgery of the Extremities.

DISEASES OF JOINTS

#Bacterial Diseases.#--In most bacterial diseases the organisms are
carried to the joint in the blood-stream, and they lodge either in the
synovial membrane or in one of the bones, whence the disease
subsequently spreads to the other structures of the joint. Organisms may
also be introduced through accidental wounds. It has been shown
experimentally that joints are among the most susceptible parts of the
body to infection, and this would appear to be due to the viscid
character of the synovial fluid, which protects organisms from
bactericidal agents in the tissues and fluids.

PYOGENIC DISEASES

The commoner pyogenic diseases are the result of infection of one or
other of the joint structures with _staphylococci_ or _streptococci_,
which may be demonstrated in the