Alignment in Total Knee Arthroplasty: Where Have We Come From and Where Are We Going?

Numerous reports have linked malaligned total knee arthroplasty (TKA) components with increased wear, poor functional outcomes, and possibly early failure due to component loosening. Consequently, proper alignment is critical to a successful outcome. This article will review: the normal mechanical alignment of the knee, classical alignment in TKA, anatomic alignment in TKA, intraoperative reference points for alignment, and the potential for new alignment schema based on the kinematic axes of knee movement. Along with our increased understanding of how the knee functions, modern total knee arthroplasty has evolved to restore a neutral mechanical axis when prostheses are implanted. Although historically the goal has been to aim to be within 3 degrees of this axis, recent reports have challenged the validity of the claim that outliers have an increased risk for revision. In addition, new alignment schemes have been developed based on the kinematic axes, but as yet we await verification of results to determine whether they increase the ability of total knee arthroplasty to provide a better-functioning and longer-lasting knee for the patient.