imary focus in the bone_ causes localised pain and tenderness,
and a limp in walking, but the first sign may be the formation of
abscess or the rapid development of articular symptoms. In such cases
skiagrams afford valuable information.

Abscess formation is an early and prominent feature, whether the
disease is of osseous or synovial origin, and sinuses are liable to
form around the joint. Outlying abscesses and sinuses are usually the
result of infection of the tendon sheaths in the neighbourhood.

_Diagnosis._--When teno-synovitis occurs independently of disease of
the ankle, the swelling is confined to one aspect of the joint. In
sarcoma of the lower end of the tibia, the swelling lacks the uniform
distribution of that met with in joint disease. In Brodie's abscess of
the lower end of the tibia there may be swelling of the ankle, but
there is an area of special tenderness on percussion over the bone.

_Treatment._--The foot is immobilised at a right angle to the leg by
splints or plaster of Paris; if articular symptoms are absent or have
subsided, a Thomas' knee splint should be applied to enable the
patient to move about without bearing his weight on the affected foot
(Fig. 125). To inject iodoform, the point of the needle is inserted
below either malleolus, and is then pushed upwards alongside of the
talus. If localised disease in one of the bones is recognised before
the joint is infected, it should be eradicated by operation.

When the disease is diffuse and resists conservative treatment,
excision should be performed, the articular surfaces of the
constituent bones being removed, and if necessary the whole of the
talus.

Amputation is only called for in adults with rapidly progressing
disease and diffuse suppuration, and in cases which have relapsed
after excision.

The other diseases of the ankle include _pyogenic_, _gonorrhoeal_,
_rheumatic_, _gouty_, and _hysterical_ affections, _arthritis
deformans_, and _Charcot's disease_. The last-named is generally
associated with a rapid and painless disintegration of the bones of
the ankle and tarsus, resulting in great deformity and loss of the
arch of the foot--sometimes associated with perforating ulcer of the
sole.

Tuberculous disease in the #tarsus#, #metatarsus#, and #phalanges# has
been considered in the chapter on Diseases of Bone.

CHAPTER X

DEFORMITIES OF THE EXTREMITIES

The origin of deformities: (1) Those arising before birth; (2)