Lateral compartment arthrosis from congenital valgus or the result of previous lateral meniscectomy can be a disabling condition. Realignment osteotomy, which may avoid or delay the need for a total knee replacement, is appropriate for young or middle-aged patients suffering from a painful valgus knee. Medium or large corrections can be managed with distal femoral lateral opening wedge osteotomy while minimal deformities are best treated with medial closing wedge tibial osteotomy.