Bioelectrical Recovery After Knee Injury in an Elite Alpine Skier: A Longitudinal 19-Frequency Bioelectrical Impedance Vector Analysis Case Report.

Return-to-play (RTP) decisions after severe knee injury in elite athletes remain challenging because functional recovery may not coincide with physiological tissue recovery. This longitudinal case report evaluated Advanced 19-Frequency Bioelectrical Impedance Vector Analysis (A19FBIVA) as a non-invasive sensor-based approach for monitoring segmental lower-limb bioelectrical changes in an elite female alpine skier following a complex right knee injury. Segmental resistance (R), reactance (Xc), phase angle (PhA), and inter-limb asymmetry were assessed with a Seca mBCA 515 analyzer at 19 frequencies (1-1000 kHz) at four time points: 5 days pre-injury, 26 days post-injury, 64 days post-injury, and 135 days post-injury. The rare pre-injury baseline enabled individualized comparison beyond contralateral symmetry. At the final late-stage rehabilitation follow-up, R in the injured lower-limb segment had normalized or improved, whereas Xc and PhA remained suppressed, indicating an observational bioelectrical pattern consistent with persistent capacitance-related impairment rather than direct evidence of localized knee-tissue healing. The uninjured limb also deteriorated during early rehabilitation, demonstrating that contralateral comparison alone may underestimate residual deficits. These findings support the exploratory concept of a 'reactance lag' and indicate that A19FBIVA may provide a useful complementary monitoring layer, alongside clinical examination, imaging, functional testing, and sport-specific assessment. Larger prospective studies are required to validate thresholds, reliability, and prognostic value.