se body and feel it roll beneath his
fingers, especially if it is lodged in the supra-patellar pouch in the
knee, or on one or other side of the olecranon in the elbow. In most
instances the patient has carefully observed his own symptoms, and is
aware not only of the existence of the loose body, but of its erratic
appearance at different parts of the joint. This feature serves to
differentiate the lesions from a torn medial meniscus in which the pain
and tenderness are always in the same spot. As the body usually contains
bone, it is recognisable in a skiagram.

[Illustration: FIG. 169.--Multiple Cartilaginous Loose Bodies from
Knee-joint.]

There are two methods of _removing the body_; the first and simpler
method is applicable when the body can be palpated, usually in the
supra-patellar pouch; it is preferably transfixed by a needle and can
then be removed through a small incision; otherwise, the joint must be
freely opened and explored, firstly to find the body and further to
remove it.

The characters of this type of loose body are remarkably constant. It is
usually solitary, about the size of a bean or almond, concavo-convex in
shape, the convex aspect being smooth like an articular surface, the
concave aspect uneven and nodulated and showing reparative changes,
healing over of the raw surface, and the new formation of fibrous
tissue, hyaline cartilage and bone, the necessary nutriment being
derived from the synovial fluid (Fig. 167). The body is sometimes found
to be lodged in a defect or excavation in one of the articular surfaces,
usually the medial condyle of the femur, from which it is readily
shelled out by means of an elevator. It presents on section a layer of
articular cartilage on the convex aspect and a variable thickness of
spongy bone beneath this.

The origin of these bodies is one of the most debated questions in
surgical pathology; they obviously consist of a portion of the articular
surface of one of the bones, but how this is detached still remains a
mystery; some maintain that it is purely traumatic; Konig regards them
as portions of the articular surface which have been detached by a
morbid process which he calls "osteochondritis dessicans."

_Multiple Chondromas and Osteomas of the Synovial Membrane._--In this
rare type of loose body, the surface of the synovial membrane is studded
with small sessile or pedunculated tumours composed of pure hyaline
cartilage, or of bone, or of transition