Reliability and validity of the Lower Limb Function Questionnaire when completed by young adult orthotic and prosthetic device users

Abstract

Purpose The Lower Limb Function Questionnaire (LLFQ) was developed as a self-report assessment of lower-limb functional ability for orthotic and prosthetic (O&P) device users to be suitable for a wide range of conditions, cultures, and ages. The measure aims to address an existing gap in tools for the assessment of functional ability in this population. The purpose of this study is to evaluate LLFQ reliability and validity in a sample of young adult O&P users. Methods Adolescents from a secondary school in Kenya completed the LLFQ twice, 6 d apart, and test–retest reliability was assessed using intra-class correlation coefficients. Validity evaluations involved Timed Up-and-Go, 6-min walk, 6-min obstacle course, and/or spatiotemporal gait assessments. Oxygen consumption was measured during walk tests. Associations between the LLFQ and each measure were evaluated using Pearson correlation coefficients for construct validity.

Results LLFQ reliability was acceptable (ICC = 0.79, 95% CIs 0.64–0.89). Construct validity was demonstrated via moderate correlation (r  >  0.60) with obstacle course distance, gait velocity, stride length, and stance/single support/double support percent of gait cycle. Conclusions Both LLFQ reliability and validity were acceptable in the sample of youth in Kenya. Further testing is required to determine applicability in other cultural contexts.

Implications for Rehabilitation

• The LLFQ may be clinically useful across a variety of cultures and conditions to provide feedback on the effectiveness of rehabilitative treatment or assistive devices for youth with lower limb impairments.

• The LLFQ may enable specific strengths and challenges to lower limb function to be identified to enable planning of well-targeted rehabilitation.

Keywords:

• low-resource
• orthotics
• outcomes measure
• prosthetics
• questionnaire
• test–retest
• validity

Acknowledgements

The authors would like to thank our universities, our partner organization at the study site, and the staff and students at the boarding school for their contributions to this investigation. Funding for travel and research was provided through private fundraising by individual researchers. The authors would like to thank those who personally donated to enable this study.

Disclosure statement

The authors report no declarations of interest.