Correction of deformity—The implant is never enough!

The basic definitions of “mechanical” and “anatomic” alignment are essential in the discussion of correction of significant varus and valgus deformities in the arthritic knee. Full length radiographs are important in understanding deformity, which is best described as a problem of the limb, not the joint. The correction of deformity is never achieved by the “purchased product” i.e. the prosthesis, but rather by the surgical technique. There is a healthy debate over what alignment should be selected for relatively un-deformed, as well as deformed limbs- the more extreme cases often help s define principles. Alignment cannot be discussed constructively without considerations of stability.