To determine the sensitivity to change and minimal clinically important difference (MCID) for the self-administered Locomotor Capabilities Index-5 (LCI-5) in people with lower limb amputation undergoing prosthetic training.

Prospective single-group observational study.

The LCI-5 was administered to 110 patients (69 males [63%]; median [interquartile range] age, 60 [48–69] years) before and after prosthetic training. The external anchor administered after the program was a 7-point Global Rating of Change Scale (GRCS) designed to quantify the effect (improvement or deterioration) of the intervention.

Test–retest reliability of the LCI-5 (n=30) was high (intraclass correlation coefficient [ICC_2,1]=0.92). The minimum detectable change at the 95% confidence level was 5.66 points. After triangulating these results with those of the mean-change approach and receiver operating characteristic (ROC) curve analysis (area under the ROC curve≥0.90), based on a different GRCS score splitting, we identified 2 cutoffs for the LCI-5: a change of 7 points, indicating the MCID, and 12 points, indicating “large improvement” in locomotor capabilities (12.5% and 21.4% of the maximum possible score, respectively).

The LCI-5 showed a high ability to detect change over time (responsiveness). The 2 proposed values (MCID of 7 points and large improvement of 12 points), based on a mix of distribution- and anchor-based approaches, represent cutoffs that can accurately identify 2 different levels of true change (as perceived by the patient) in locomotor capability after prosthetic training.