Medicare Functional Classification Levels (K-levels) are widely used to grade community mobility in people with transfemoral amputation (TFA), yet their relationship with quantitative gait biomechanics remains unclear. To compare gait kinematics and kinetics between K2 and K3 individuals with unilateral TFA, and between prosthetic and sound limbs. Seventeen adults with unilateral TFA (8 K2, 9 K3) walked on an instrumented treadmill. Joint-angle and joint-moment waveforms (hip, knee, ankle) were compared using Statistical Parametric Mapping (SPM; α = 0.05). Participant-level k-means clustering was performed on swing-phase peaks from both limbs (8 features in total), with silhouette analysis used to select the number of clusters. SPM detected no K2–K3 differences in any joint-angle waveform for either limb. On the prosthetic limb, between-group differences were limited to joint-moment regions: hip moment at 55–58% and ankle moment at 50–61% of the gait cycle; no between-group differences were observed on the sound limb. Prosthetic-versus-sound comparisons revealed multiple significant intervals across the gait cycle in hip, knee, and ankle angles and moments. Clustering supported K = 2 (average silhouette = 0.27), yielding Cluster A (n = 10) and Cluster B (n = 7) that did not align with K-levels; clusters differed notably in hip swing peaks (e.g., prosthetic hip flexion p = 0.001). K2–K3 classification showed minimal association with gait waveform features, whereas robust limb asymmetries and distinct biomechanical phenotypes were evident. These findings support complementing K-levels with quantitative, side-specific biomechanical assessment when characterizing TFA gait.
Tamashiro et al. (Thu,) studied this question.