1. Stainless steel mould arthroplasty of the knee is described and a ten-year follow-up study of sixty-two operations is reported. Fifty-four were for rheumatoid arthritis and eight for osteoarthritis.

2. Forty-nine of the sixty-two joints retained mobility, six had become ankylosed and five were later arthrodesed ; two limbs were amputated. The forty-nine mobile knees included twenty-seven which were painless at all times, and fourteen in which only an occasional twinge was felt.

3. The range of movement was increased in twenty-two joints as compared with the state before operation, diminished in twelve and unaltered in five. In ten knees measurements before operation were not available.

4. Flexion deformity, swelling, stability and function were improved in a significant number of joints.

5. Patients suffering from active rheumatoid arthritis often found that the joint operated upon no longer took part in generalised flares of the disease.