Motor-Sparing Regional Analgesia in Frail and Sarcopenic Older Adults Undergoing Total Knee Arthroplasty: From Anatomy to Clinical Decision-Making—A Narrative Review

Total knee arthroplasty (TKA) is increasingly performed in older adults, a population with a growing prevalence of frailty and sarcopenia. Analgesic strategies focused mainly on pain reduction may overlook mobility, functional independence, fall prevention, and delirium risk, making motor preservation a central goal of perioperative care. This narrative review examines the anatomical basis, clinical evidence, and practical application of motor-sparing regional analgesia for older adults undergoing TKA, with emphasis on frailty, sarcopenia, and mobility-centred recovery, synthesising current evidence on established, emerging, and experimental techniques. Evidence was classified as geriatric-specific, older-enriched mixed-age, or mixed-age adult. Most technique-specific evidence derives from cohorts that included younger adults; only two small randomised trials reported cohorts composed exclusively of patients aged ≥65 years, and no regional-analgesia trial stratified outcomes by frailty or sarcopenia. A pragmatic clinical decision framework was developed to support individualised strategy selection in frail and sarcopenic patients. Current evidence supports adductor canal block combined with local infiltration analgesia as the foundation of motor-sparing analgesia after TKA; supplementary techniques such as iPACK, popliteal plexus block, genicular nerve block, and anterior femoral cutaneous nerve block may further optimise sensory coverage while preserving quadricep strength, whereas femoral nerve block produces predictable motor impairment and appears less suitable for this population. The existing literature remains largely focused on pain scores and opioid consumption, while mobility-related outcomes are infrequently reported. Direct evidence for falls, near-falls, delirium, discharge destination, functional independence, and long-term mobility remains sparse or absent. Successful analgesia after TKA should be defined not only by pain relief but by preservation of mobility and functional recovery, and future research should prioritise frailty-specific, mobility-centred outcomes.