Differences in Measures of Strength and Dynamic Balance Among Individuals With Lower-Limb Loss Classified as Functional Level K3 Versus K4.

Objective: For individuals with lower-limb loss, functional mobility (ie, K-level) classification can be subjective. Performance-based outcome measures improve the objectivity of K-level assignment; therefore, this study aimed to determine differences in functional strength- and dynamic balance-based outcome measures performance between K3- and K4-classified adults with lower-limb loss.

Design: Prosthetists used subjective information and prosthetic componentry to determine K-levels before outcome measures testing for adults with a unilateral transtibial (n = 50) or transfemoral amputation (n = 17). Outcome measures (ie, 5-Times Sit-to-Stand Test, Figure-of-8 Walk Test, 360-degree Turn Test, and modified Four-Square Step Test) were administered by a blinded examiner. Univariate analyses of variance were used to evaluate between-subgroup differences.

Results: K4-classified participants with a unilateral transfemoral amputation performed better on all outcome measures when compared with K3-classified peers, whereas K4-classified individuals with a transtibial amputation performed better on the modified Four-Square Step Test compared with K3-classified peers (P < 0.050).

Conclusions: K4-classified individuals demonstrated greater lower-limb functional strength and better dynamic balance compared with K3-classified peers. To assist with K-level classification, clinicians should consider selecting outcome measures that objectively differentiate between K-levels (ie, modified Four-Square Step Test for those with a unilateral transtibial or transfemoral amputation; 5-Times Sit-to-Stand Test, Figure-of-8 Walk Test, and 360-degree Turn Test for those with a transfemoral amputation).