Motor-Sparing Regional Anesthesia for Knee Surgery: The Adductor Canal Block, the Nerve to the Vastus Medialis, and the IPACK Block

Effective analgesia after knee surgery has to be reconciled with the demands of enhanced recovery pathways, in which early ambulation and same-day or next-day discharge are explicit goals. The femoral nerve block, long the reference technique, achieves the first aim at the cost of the second: quadriceps weakness delays mobilization and raises concern about falls. Over the past decade the field has therefore reorganized itself around the idea of motor-sparing blockade — placing local anesthetic where the sensory supply of the knee can be interrupted while the motor supply to the quadriceps is left substantially intact. This review examines the three techniques that define current practice. The adductor canal block, and its more proximal variant the femoral triangle block, target the saphenous nerve and the articular branches travelling with the nerve to the vastus medialis; the accumulated randomized evidence shows analgesia broadly equivalent to the femoral nerve block with better preservation of quadriceps strength. The nerve to the vastus medialis has emerged as a structure of interest in its own right, since it carries both articular afferents to the anteromedial capsule and motor fibres, so that the balance between analgesia and strength depends on precisely where along the canal the injection is placed. The IPACK block addresses the posterior capsule, a territory none of the anteromedial techniques reaches. We summarize the anatomical basis of each block, the randomized and meta-analytic evidence supporting them, and the practical questions — injection site, volume, adjuvants, and the interaction with surgical local infiltration analgesia — that remain unsettled.