In examining a joint in order to determine the degree of stiffness, taking for an example a knee-joint, because the knee is the articulation most commonly concerned and the one about which more mistakes are probably made than any other articulation, there are some practical details which may be worth pointing out, as they are of importance.

The main difference felt upon manipulation in a joint which is in a condition of bony ankylosis and one which is merely stiff from adhesions or matting is, of course, that the former is rigid in its stiffness like a bar of iron or wood, and the latter gives a sensation of 'spring' in the line of the joint on attempts at bending. In some cases the signs of the two conditions of true ankylosis and extreme rigidity from adhesions approach so nearly to one another that it is only by the most careful manipulation that they can be differentiated. It is by attempts at flexion alone of any joint that a reliable judgment in this respect can be arrived at; the evidence of attempts at extension are nugatory and deceptive. In testing the rigidity of a joint by flexion the following points are essential to be observed in different cases: (1) The proximal bone must lie along its whole length upon a flat surface (e.g. a kitchen table) to which it can be firmly applied by pressure of the hands of an assistant or some other means.

(2) The end of the flat surface must lie exactly across the middle of the affected articulation, so that when pressure is made upon the distal bone the stress of strain comes accurately upon the line of the joint.

(3) The pressure upon the distal bone should be such as is likely to elicit the sense of 'spring' in the articulation most correctly; to this end the distal bone should not be grasped in the hand and forcibly bent continuously, but the hand of the manipulator should merely be laid upon the distal portion of the limb and a decided but not too sudden impact given; a sense of spring in the line of the joint will in this way be much more easily determined than by the firm grasp and forcible attempts at flexion usually employed, since the forcible attempts referred to are liable to convey a sense of spring which involves not the joint alone but the whole limb.

By the above method it is almost impossible to be deceived as to the nature of the stiffness even in the most difficult cases. In an ordinary way the following plan will suffice. One hand of the manipulator should be placed on the flexor side of the joint, say, for an example, the knee, the limb being poised upon the hand thus placed; the opposite hand taking the leg just below its middle, attempts are made to flex the knee whilst upward pressure is made by the hand which underlies the joint. Any material spring that there may be in the articulation will be felt immediately, not by the hand which is on the leg, but by that which is beneath the joint. By such a method of examination a very slight amount of spring in an articulation can be appreciated by any person possessing an average acuteness of sensation, and in a case of stiff joint in which there is a sufficient amount of spring to be appreciated in this way there is a strong chance, provided that the other conditions to which I shall refer presently are favourable, of a cure being effected by discreet forcible manipulations.

It is stated that a valuable indication of the existence of bony ankylosis on the one hand and mere stiffness on the other is the absence or presence of pain after violent manipulation under an anaesthetic, the subsequent occurrence of pain in the line of the articulation being held to be in favour of the absence of bony ankylosis. No reliance can be placed on this test, as in certain cases of bony ankylosis following upon tubercle manipulations are always followed by pain of variable severity. Of course, the proper appreciation of minute differences in rigidity must to a great extent be dependent upon the delicacy of the sense of touch in the manipulator, but in a general way the distinction is not difficult.