Personalized alignment in TKA: current concepts

Background: Total knee arthroplasty (TKA) traditionally utilized mechanical alignment (MA) to achieve a neutral hip-knee-ankle (HKA) angle of 180°. Although MA provides high implant survivorship, a significant proportion of patients report residual pain and functional dissatisfaction. Recent anatomical studies demonstrate that native coronal alignment is highly variable, leading to the development of personalized alignment strategies that prioritize individual kinematics over systematic neutral positioning.

Objective: This review aims to define the principles of personalized alignment concepts in TKA, including kinematic, inverse kinematic, restricted kinematic, and functional alignment, while summarizing current clinical outcomes and surgical methodologies.

Key Points: Kinematic alignment (KA) aims to restore pre-arthritic joint lines and ligamentous tension by resurfacing the femur and tibia based on individual anatomy. To mitigate risks of aseptic loosening associated with extreme varus, restricted KA (rKA) limits bone resections to within ±5° of the mechanical axis and HKA to within ±3° of neutral. Inverse kinematic alignment (IKA) prioritizes native tibial joint line obliquity, adjusting femoral resections to achieve gap balance. Functional positioning utilizes robotic-assisted technology to fine-tune implant placement based on intraoperative soft tissue tension. Comparative studies indicate that KA may offer superior patient-reported outcomes, such as the Forgotten Joint Score, compared to MA, though long-term data for restricted and inverse techniques remain limited.

Conclusion: Personalized alignment strategies represent a shift toward restoring patient-specific kinematics in TKA. While early clinical results are encouraging, long-term follow-up is essential to evaluate the impact of non-neutral alignment on implant longevity and aseptic failure rates.