1. The technique of the intra-articular surgery employed by the late Mr K. H. Pridie for osteoarthritis of the knee is described.

2. The results of sixty-two operations in sixty patients are analysed. The results in forty-eight knees (77 per cent) were pleasing to the patient. Forty knees (64 per cent) were rated as good at review.

3. The operation is most suitable for relatively active healthy people whose disability warrants a comparatively painful operation and lengthy rehabilitation.

4. The operation was most successful for relieving pain and improving stability. Functional improvement was less.

5. Results were remarkably permanent. The knees showed little tendency towards further deterioration.

6. Most of the bad results were associated with removal of the patella. A possible technical reason for this has been discussed.