Despite their age, patients younger than 50 years who have collapse of their femoral condyles caused by steroid associated avascular necrosis have few options except total knee arthroplasty. There have been no specific reports of the results of total knee replacements for this disease. Between 1980 and 1993, 31 porous coated anatomic total knee replacements were performed in 21 patients younger than 50 years of age with avascular necrosis of the femoral condyles and tibial plateaus. There were 17 women and 4 men, with an average age of 36 years (range, 22-48 years). Seventeen of 21 patients had systemic lupus erythematosus, and all patients had a history of corticosteroid use. Patients underwent a complete clinical and radiographic evaluation at final followup that averaged 8.2 years (range, 2-16 years). Overall, there were 17 good and excellent results (55%). Eleven knees were revised for aseptic loosening (37%), and 3 additional knees (10%) ultimately were revised for deep sepsis. All 6 knees in patients with no diagnosis of systemic lupus erythematosus had excellent clinical results. There were only 11 of 25 successful outcomes (44%) in the patients with systemic lupus erythematosus. There were no differences in results when patients were stratified by degree of steroid use, cemented versus cementless fixation, or activity level.