Like other hypertrophies on a free surface, they tend to become pedunculated, and so acquire a limited range of movement.  The pedicle may give way and the body become free.  In this condition it may wander about the joint, or lie snugly in one of its recesses until disturbed by some sudden movement.  A loose body free in a joint is capable of growth, deriving the necessary nutriment from the surrounding fluid.  The size and number of the bodies vary widely.  Single specimens have been known to attain the size of the patella.  The smaller varieties may number considerably over a hundred.

[Illustration:  FIG. 167.—­Loose Body from Knee-joint of man aet. 25.  Natural size.

a = Convex surface. b = Concave surface.]

In arthritis deformans a rarer type of loose body is met with, a portion of the lipping of one of the articular margins being detached by injury.  In Charcot’s disease, bodies composed of bone are formed in relation to the capsular and other ligaments, and may be made to grate upon one another.

The clinical features in this group are mainly those of the disease which has given rise to the loose bodies, and it is exceptional to meet with symptoms from impaction of the body between the articular surfaces.  Treatment is to be directed towards the primary disease in the joint, as well as to the removal of the loose bodies.

[Illustration:  FIG. 168.—­Multiple partially ossified Chondromas of Synovial Membrane, from Shoulder-joint, the seat of arthritis deformans, from a man aet. 35.]

Loose Bodies in Joints which are otherwise healthy.—­It is in joints otherwise healthy that loose bodies causing the classical symptoms and calling for operative treatment are most frequently met with.  They occur chiefly in the knee and elbow of healthy males under the age of thirty.  The complaint may be of vague pains, of occasional cracking on moving the joint, or of impairment of function—­usually an inability to extend or flex the joint completely.  In many cases a clear account is given of the symptoms which arise when the body is impacted between the articular surfaces, namely, sudden onset of intense sickening pain, loss of power in the limb and locking of the joint, followed by effusion and other accompaniments of a severe sprain.  On some particular movement, the body is disengaged, the locking disappears, and recovery takes place.  Attacks of this kind may recur at irregular intervals, during a period of many years.  On examining the joint, it is usually found to contain fluid, and there may be points of special tenderness corresponding to the ligaments that have been overstretched.  In cases in which there has been recurrent attacks of locking, the ligaments become slack, the joint is wobbly, and the quadriceps is wasted.  The patient himself, or the surgeon, may discover the loose body and feel it roll beneath his fingers, especially if it is lodged in the supra-patellar