Loose bodies may be found in the articulations, particularly in the knee and elbow, under the circumstances just described; but we often find others of a different structure loose within the capsule, which may be throughout smooth and apparently healthy. These bodies are extremely variable in size, generally rounded or oval, with a polished surface; many of the smallest present the character of fibro-cartilage or cartilage; the larger are often more or less modulated, very firm and gristly, and sometimes contain a considerable nucleus of bony matter. The articular ends of the bones are occasionally more or less misshapen by the formation around them of knobs of adventitious osseous substance. The disease is common in the knee; and patients frequently go about for years, who will tell you that they have something rolling within the joint, which will often be found on examination to be actually the case. It is obvious that loose bodies in the joint must prove an obstacle to easy progression; and the smaller ones seem to be particularly so, probably from becoming easily entangled by different parts of the articular apparatus. However difficult it may be to account for the cause of these formations, the means by which they may get within the articulation seems obvious enough. If a small knob of coagulated lymph should form on the inner aspect of the membrane, the point of attachment, as has already been noticed, might gradually become narrower, from the motions of the joint or other causes, till the connection were severed. But there is reason to believe that many of the substances found loose in the joints are formed altogether in the cellular tissue without the capsule; for it is difficult to conceive that they can increase in size, or take on the ossific action in their centre, by an act of independent vitality, after they have been separated from the surrounding parts. Accordingly, dissection has occasionally disclosed loose bodies within the knee-joint, and others of just the same structure outside the synovial membrane, which was however protruded by their pressure, and appeared to connect some of them by a pedicle only, ready to break and allow the foreign body, with its covering of the membrane, to fall into the cavity of the articulation. AFFECTIONS OF SYNOVIAL POUCHES OR BURSÆ. Bursæ are lined by a membrane, greatly resembling the synovial in appearance, function, and disease. They are frequently the seat of inflammation of an acute character; but in most instances the action is of short duration, and generally terminates in an increase and accumulation of the secreted fluid. The attendant pain is very severe, and much increased by any motion of the neighbouring parts.