Pediatric lower limb differences (LD) include a wide spectrum of congenital, developmental and acquired causes of limb deficiencies, deformities, and length discrepancies. Congenital lower-limb deficiencies, including the absence or shortening of a limb or part of a limb, have a reported incidence of 2–7 in 10 000 births . About 1 in 1000 people have a clinically relevant length discrepancy greater than 2 centimetres . Lower limb deformities and length discrepancies are associated with a number of developmental conditions (e.g., Blount’s disease), or may be acquired as a consequence of partial or complete injuries to the growth plate secondary to fractures, infection or neoplasms. These conditions are associated with abnormal gait and increased biomechanical effort [3–5], altered appearance of the limb, and psychosocial consequences [3, 6]. Children with LD are faced with a variety of treatment options and often undergo multiple interventions throughout their childhood; yet we know very little about how this may impact their health related quality of life (HRQL) . The benefits of these interventions, let alone their comparative effectiveness, are poorly quantified because there are no validated outcome measures developed for this population.
The International Classification of Functioning, Disability and Health (ICF)  is a useful framework to conceptualize the consequences and outcomes of LD, illustrated in Fig. 1. The management and evaluation of care should be informed by “multidimensional assessment leading to targeted interventions based on patient (parent) perceived needs” . The ultimate goal of treating children with LD is to improve HRQL, optimizing function and maximizing participation, by addressing the physical, social and psychological effects of their LD. Research on pediatric LD has focused on the ICF domain of Body Functions and Structures  such as radiographic measures of limb alignment and length, post-operative complications, and time to heal . Although these are important markers of the technical success of an intervention that address the physical impairments, one cannot assume that these correspond with HRQL outcomes that matter most to children/parents and are aligned with their priorities and goals. These are better captured in the ICF domains of Activity and Participation, using patient-reported outcome measures (PROMs) that are designed to measure these outcomes . To date, generic measures of health status or HRQL (e.g., Child Health Questionnaire, ; PODCI ) have shown limited discriminative ability and responsiveness for this population, [7, 6, 14–16] highlighting the imperative for a more meaningful PROM for children with LD.
The Priority Framework for Outcome Assessment [17, 18], depicted in Fig. 2, illustrates that to be meaningful to an individual, an outcome measure must incorporate their priorities and goals. To affect HRQL, interventions must address a patient’s goals, and effectiveness must be judged based on whether these goals were met. The Gait Outcomes Assessment List (GOAL) [19, 20] questionnaire is a multi-dimensional, self-administered child- and parent-report that was developed using the Priority Framework as its conceptual framework. The GOAL was created to evaluate outcomes based on the broad range of children’s and parents’ goals for gait related interventions for children with cerebral palsy, with a view to ultimately applying it to other childhood conditions associated with lower extremity impairments. The GOAL is a hybrid measure, combining the specificity of an individualized measure that identifies patient specific priorities or goals for treatment, with the standardization of a fixed item PROM. While individualized measures such as the Canadian Occupational Performance Measure (COPM)  and Goal Attainment Scaling (GAS) [22, 23] are well documented in pediatric rehabilitation outcomes research, most studies also employ a fixed item functional measure as a parallel tool  to evaluate intervention effectiveness at a group level and/or to provide predictive or discriminative information . A questionnaire that combines the benefits of individualization and standardization is uniquely comprehensive and reduces the need to administer multiple questionnaires to patients.
The original version of the parent- and child-reported GOAL questionnaire  used as the starting point in this study, consists of 50 items across seven domains: (A) Activities of Daily Living (ADL) & Independence, (B) Gait Function & Mobility, (C) Pain/Discomfort/Fatigue, (D) Physical Activities, Sport & Recreation, (E) Gait Appearance, (F) Use of Braces & Assistive Devices, and (G) Body Image & Self-Esteem. Domains associated with tasks or activities use a 7-point ordinal scale anchored from 0: “extremely difficult/impossible” to 6: “no problem at all” with a 4-point modifier on how much assistance (from 0: “total” to 3: “independent”) is required to accomplish each task or activity. Symptoms such as pain or fatigue are rated on a 6-point scale of frequency, from 0: “every day” to 5: “none of the time” as well as their intensity (0: “severe” to 2: “mild”). Domains that examine the respondent’s feelings use a 5-point ordinal scale from 0: “very unhappy” to 4: “very happy. Item scores are standardized (raw item score divided by total possible score for that item, multiplied by 100). Domain scores are the average of the standardized item score for each item in that domain, and the total score is the average of all the standardized item scores, reported from 0 to 100.
A key feature of the GOAL questionnaire is that for each item, the respondent also rates how important a goal it is to improve on that item using a 5–point scale from not a goal to extremely important. These importance ratings do not contribute to the total or domain score, but highlight, for each individual, which items are most important for improvement. Respondents may also specify additional goals and rate the importance of improving these.
Although the GOAL was developed and has been validated for children with ambulatory cerebral palsy , its focus on patient priorities and coverage of all domains of the ICF associated with gait-related problems  provides the foundation for developing a parallel measure for pediatric LD. Given that CP with its neurologic impairments is sufficiently different from LD, some of the content of the GOAL might not be as relevant to children with LD, and some important content to LD might be missing.
The aims of this study were to (i) evaluate the suitability of the items of the GOAL and its sensibility (face and content validity, comprehensibility, clarity of instruction, appropriateness of response scale, and ease of usage) from the perspective of children with LDs, their parents, and health care professionals (HCPs) with expertise in this population, and to (ii) adapt the GOAL based on the input of these stakeholders to create the GOAL-LD. Permission to proceed with development of the GOAL-LD was granted by the GOAL’s developer (UG Narayanan, oral communication, September 2011).