[Illustration: FIG. 113.--Thomas' Flexion Test, showing angle of flexion at diseased (left) hip.] _Swelling_ is seen on the anterior aspect of the joint; it may fill up the fold of the groin and push forward the femoral vessels. It is doughy and elastic, but may at any time liquefy and form a cold abscess. Swelling about the trochanter and neck of the bone may be estimated by measuring the antero-posterior diameter with callipers, and comparing with the sound side. Swelling on the pelvic aspect of the acetabulum can sometimes be discovered on rectal examination. _Third Stage._--This probably corresponds with caries of the articular surfaces, since pain is now a prominent feature, and there are usually startings at night. The attitude is one of adduction, inversion, flexion, and apparent or real shortening of the limb (Fig. 114). The _flexion_ is usually so pronounced that it can no longer be concealed by lordosis, so that when the patient is recumbent, although the spine is arched forwards, the limb is still flexed both at the hip and at the knee; with the spine flat on the table, the flexion of the thigh may amount to as much as a right angle. The _adduction_ varies greatly in degree; when it is slight, as is most often the case, the toes of the affected limb rest on the dorsum of the sound foot. When moderate, it is compensated for by raising the pelvis on the affected side, with _apparent shortening_ of the limb, this being the result of an effort on the part of the patient to restore the normal parallelism of the limbs, the sound limb being abducted to the same extent as the affected limb is adducted. It is important to recognise the cause of this shortening, as it can be corrected by treatment. As a result of the obliquity of the pelvis, the patient, when erect, exhibits a lateral curvature of the spine with the dorso-lumbar convexity to the sound side. [Illustration: FIG. 114.--Tuberculous Disease of Left Hip: third stage, showing adduction and shortening.] When adduction is pronounced, the patient is unable to restore the normal parallelism of the limbs, and the knee on the affected side may cross the sound limb. There is a deep groove at the junction of the perineum and thigh, great prominence of the trochanter, and the pelvis may be tilted to such an extent that the iliac crest comes into contact with the lower ribs. As a result of the pressure of the carious articular surfaces against one another, the acetabulum is enlarged and the upper end of the femur is drawn gradually upwards and backwards within the socket. Examination will then reveal the existence of a variable amount of _actual shortening_; it will also be found that the trochanter is displaced above Nélaton's line, while above and behind the trochanter there is a prominent hard swelling corresponding to the enlarged acetabulum. There may, therefore, be a combination of real and apparent shortening together amounting to several inches (Fig. 115).