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; König 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 stages between cartilage and bone. They are pearly white in colour, pitted and nodular on the surface, rarely larger than a pea, although when compressed they may cake into masses of considerable size. With the movements of the joint many of the tumours become detached and lie in the serous exudate excited by their presence. They are found also in the diverticula of the synovial membrane, in the shoulder in the downward prolongation along the tendon of the biceps, in the hip in the bursal extension beneath the psoas.

The patient complains of increasing disability of the limb, movements of the joint becoming more and more restricted and painful. There is swelling corresponding to the distended capsule of the joint, and on palpation the bodies moving under the fingers yield a sensation as of grains of rice shifting in a bag. If the bodies are so numerous as to be tightly packed together, the impression is that of a plastic mass having the shape of the synovial sac. The stiffness and the cracking on movement may suggest arthritis deformans, but the X-ray appearances make the diagnosis an easy one. We have observed two cases of this affection in the knee-joint of adult women, one in the shoulder-joint of an adult male ([Fig. 168]), and Caird has observed one in the hip. The treatment consists in opening the joint by free incision and removing the bodies.

Displacement of the menisci of the knee is referred to with injuries of that joint.

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