Clinicians involved in prosthetic prescription may consider including the TUG, 10MWT, AMPPRO, and 6MWT during their clinical evaluations to help differentiate between individuals of higher functional mobility. The LCI and PEQ-MS may be less useful in classifying individuals as K3 versus K4 because of a ceiling effect.

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).