This 2020 annotation by Oussedik et al. reviews the three principal alignment philosophies in TKA: mechanical, kinematic, and functional. It defines what each strategy optimizes, what each sacrifices, and how computer and robotic assistance has made a hybrid approach reproducible. The paper proposes functional alignment as a way to achieve mechanically sound, soft tissue-friendly targets within a coronal safe zone of 0° ± 3°.
TKA dissatisfaction rates have driven the field to question whether neutral mechanical alignment — the standard for decades. Is actually optimal for every patient. The problem is straightforward: constitutional varus knees have native MCLs calibrated to an oblique joint line. Force that line horizontal and you tension the MCL, which means release it or accept a stiff, imbalanced knee.
When robotic assistance is available, functional alignment lets you individualize component position in all three planes. Accepting up to 3° of tibial varus to close a tight medial gap. While keeping the overall HKA within the 0° ± 3° safe zone. No release needed.
Without navigation or robotics, do not attempt non-neutral targets. The authors are explicit: stick to mechanical alignment with correct soft tissue releases, because you cannot reproducibly hit individualized targets by hand. The authors caution that functional alignment still lacks long-term outcome data, and its dependence on expensive technology limits widespread adoption.
This 2020 annotation by Oussedik et al. reviews the three principal alignment philosophies in TKA: mechanical, kinematic, and functional. It defines what each strategy optimizes, what each sacrifices, and how computer and robotic assistance has made a hybrid approach reproducible. The paper proposes functional alignment as a way to achieve mechanically sound, soft tissue-friendly targets within a coronal safe zone of 0° ± 3°.
TKA dissatisfaction rates have driven the field to question whether neutral mechanical alignment — the standard for decades. Is actually optimal for every patient. The problem is straightforward: constitutional varus knees have native MCLs calibrated to an oblique joint line. Force that line horizontal and you tension the MCL, which means release it or accept a stiff, imbalanced knee.
When robotic assistance is available, functional alignment lets you individualize component position in all three planes. Accepting up to 3° of tibial varus to close a tight medial gap. While keeping the overall HKA within the 0° ± 3° safe zone. No release needed.
Without navigation or robotics, do not attempt non-neutral targets. The authors are explicit: stick to mechanical alignment with correct soft tissue releases, because you cannot reproducibly hit individualized targets by hand. The authors caution that functional alignment still lacks long-term outcome data, and its dependence on expensive technology limits widespread adoption.