Mechanical alignment can still be an optimal target in total knee arthroplasty for severe varus knee

The aim of this review was to investigate which alignment strategy provides the most appropriate target in total knee arthroplasty (TKA) for severe varus deformity, taking into account age-related skeletal changes, ligament balance, and implant longevity. Relevant radiographic, biomechanical, intra-operative, and clinical studies were reviewed to clarify how age-related deformity, soft tissue conditions, and post-operative alignment influence outcomes in varus knees undergoing TKA. Radiographic analyses show that lower limb deformity progresses with aging and osteoarthritis, making it difficult to identify the constitutional alignment based on pre-operative morphology. Intra-operative findings reveal that the medial structures are not necessarily contracted, whereas lateral laxity increases with varus severity. Biomechanical simulations indicate that varus alignment exceeding 6° results in a marked increase in medial contact stress, and clinical studies report inferior outcomes and a higher risk of tibial loosening in such cases. Reconstruction in neutral mechanical alignment without excessive medial release provides stable kinematics and satisfactory clinical outcomes, even in severe varus knees. In patients with advanced varus deformity, aiming to reproduce the native alignment is neither practical nor beneficial because of age-related skeletal changes and altered ligament balance. Mechanical alignment within 3° of neutral, achieved without excessive medial release, remains a reasonable and safe target that minimizes implant stress and ensures long-term stability. Alignment beyond 6° varus should be avoided. • In advanced varus deformity, it is difficult to determine constitutional alignment based on pre-operative bone morphology. • The lateral structures are often lax, making it challenging to restore native ligament balance. • Leaving a post-operative varus alignment greater than 6° is not recommended. • Mechanical alignment without medial release may be considered a viable strategy.