1. We have reported our experience in fifty-two patients with arthrogryposis multiplex congenita.

2. The nature of the disorder, its possible cause, the clinical features and differential diagnosis are discussed.

3. Early management is described with special reference to the infant, his parents, and general principles of selection and timing. The treatment of the individual deformities which commonly occur is outlined.

4. We have emphasised that lower limb deformities should be treated vigorously in the first year, whereas in the upper limb treatment is better delayed until an accurate assessment can be made.

5. Correction in the young child should be by soft-tissue release rather than by osteotomy.

6. Prolonged splinting after operation is necessary.

7. Severe weakness may dominate the problem and make operation unrewarding.

8. The intelligence, determination and adaptability of these children flatters even modest surgical success.

1. The clinical features in nineteen patients with structural defects of the pars interarticularis are compared with the findings in twenty-two patients with degenerative changes in the lumbar spine, and are shown to be essentially the same.

2. It is suggested that both structural defects and degenerative changes give rise to mechanical instability of the lumbar spine. This puts an increased load on the posterior vertebral soft tissues and gives rise to a characteristic picture, the features of which are described.

3. The signs and symptoms of root compression may be superimposed on this picture, and when this is the case, decompression of the nerve roots should be undertaken in addition to spinal fusion, which is suggested as the logical treatment.

4. After fusion, with decompression when indicated, 50 per cent of the patients were completely relieved of their symptoms and 87 per cent derived worthwhile benefit.