Sixteen total knee arthroplasties performed between 1977 and 1985 in 13 patients with prior ipsilateral hip arthrodesis or ankylosis were studied to determine the preferred sequence and long-term follow-up of procedures in this clinical setting. Twelve of 16 underwent fusion takedown and total hip arthroplasty prior to knee replacement. The average age at total knee arthroplasty was 52.7 years and the average time from hip fusion to total knee arthroplasty was 36.3 years. Mean follow-up after total knee arthroplasty was 5.5 years (range, 2.3 to 10 years). The Hospital for Special Surgery knee score increased from a mean of 31.8 preoperatively to 72.2 after surgery. In patients who had conversion of the hip fusion prior to knee replacement, knee scores were 28 before and 72.5 after both procedures. Patients who retained their hip fusion had mean scores of 43.5 and 72.1, respectively. None of the knees has been removed and 14 of 16 had no pain at last follow-up. One had mild pain and one had moderate pain attributed to pes anserine bursitis. Although the numbers are small, this experience reveals that takedown of the fusion with total hip arthroplasty is an effective technique before performing the knee replacement. Though successful in some instances, the experience is too small to show that if hip fusion is in good position, knee replacement without fusion takedown is acceptable.