BACKGROUND Distal femoral varus osteotomy is a procedure that is performed for the treatment of lateral-compartment osteoarthritis of the knee as well as for correction of the associated valgus deformity. However, its role remains controversial and its efficacy in the treatment of associated patellofemoral arthritis has not been well studied. The purpose of the present study was to evaluate the outcome after distal femoral osteotomy performed for the treatment of painful genu valgum and to assess the influence of patellofemoral arthritis on the results. METHODS Thirty patients (thirty knees) were managed with distal femoral varus osteotomy for the treatment of noninflammatory lateral-compartment arthritis of the knee associated with a valgus deformity. Twelve knees had isolated lateral-compartment arthritis, ten had mild-to-moderate degenerative changes in the other two compartments, and eight knees had severe patellofemoral arthritis in addition to lateral-compartment disease. The osteotomy site was fixed with a 90 degrees blade-plate. After a mean duration of follow-up of ninety-nine months, all patients were evaluated with use of the Hospital for Special Surgery knee-rating system and a physical examination. RESULTS At the time of the most recent follow-up, twenty-five patients (83%) had a satisfactory result and two had a fair result according to the Hospital for Special Surgery rating system. The remaining three patients had had a conversion to a total knee arthroplasty. With conversion to total knee arthroplasty as the end point, the cumulative ten-year survival rate for all patients was 87% (95% confidence interval, 69% to 100%). Improvement in patellar tracking, which persisted at the time of the latest follow-up, was observed in seven of the eight knees with associated severe patellofemoral arthritis. CONCLUSIONS Distal femoral varus osteotomy with blade-plate fixation can be a reliable procedure for the treatment of lateral-compartment osteoarthritis of the knee associated with valgus deformity. The result of the osteotomy does not appear to be affected by the presence of severe patellofemoral arthritis.