Tumours and Cysts
New growths taking origin in the synovial membrane are rare, and are not usually diagnosed before operation. They are attended with exudation into the joint, and in the case of sarcoma the fluid is usually blood-stained. If the tumour projects in a polypoidal manner into the joint, it may cause symptoms of loose body. One or two cases have been recorded in which a cartilaginous tumour growing from the synovial membrane has erupted through the joint capsule and infiltrated the adjoining muscles. Multiple cartilaginous tumours forming loose bodies are described on [p. 544].
Cysts of joints constitute an ill-defined group which includes ganglia formed in relation to the capsular ligament. Cystic distension of bursæ which communicate with the joint is most often met with in the region of the knee in cases of long-standing hydrops. It was suggested by Morrant Baker that cystic swellings may result from the hernial protrusion of the synovial membrane between the stretched fibres of the capsular ligament, and the name “Baker's cysts” has been applied to these.
In the majority of cases, cysts in relation to joints give rise to little inconvenience and may be left alone. If interfered with at all, they should be excised.
Loose Bodies
It is convenient to describe the varieties of loose bodies under two heads: those composed of fibrin, and those composed of organised connective tissue.
Fibrinous Loose Bodies (Corpora oryzoidea).—These are homogeneous or concentrically laminated masses of fibrin, sometimes resembling rice grains, melon seeds, or adhesive wafers, sometimes quite irregular in shape. Usually they are present in large numbers, but sometimes there is only one, and it may attain considerable dimensions. They are not peculiar to joints, for they are met with in tendon sheaths and bursæ, and their origin from synovial membrane may be accepted as proved. They occur in tuberculosis, arthritis deformans, and in Charcot's disease, and their presence is almost invariably associated with an effusion of fluid into the joint. While they may result from the coagulation of fibrin-forming elements in the exudate, their occurrence in tuberculous hydrops would appear to be the result of coagulation necrosis, or of fibrinous degeneration of the surface layer of the diseased synovial membrane. However formed, their shape is the result of mechanical influences, and especially of the movement of the joint.
Clinically, loose bodies composed of fibrin constitute an unimportant addition to the features of the disease with which they are associated. They never give rise to the classical symptoms associated with impaction of a loose body between the articular surfaces. Their presence may be recognised, especially in the knee, by the crepitating sensation imparted to the fingers of the hand grasping the joint while it is flexed and extended by the patient.
The treatment is directed towards the disease underlying the hydrops. If it is desired to empty the joint, this is best done by open incision.