Translate and cross-culturally adapt the original English version of the lower extremity functional scale into the Sinhalese version

INTRODUCTION

The complementary tomography, physical examination, and clinical evaluation are thought inadequate to establish the level of function of an individual, especially an athlete, after injury or surgery.^[1] Precise functional assessment has been demonstrated and proven evidently to be effective in rehabilitation and administering treatment primarily focused on individual disabilities rather than relying merely on clinical assessments derived from diagnostic tests.^[2] Assessing patients’ and athletes’ awareness of their quality of life (QOF), along with monitoring enhancements in their clinical and functional status, is substantially becoming a standard practice in both, scientific and clinical societies.^[3,4] Physical function is commonly assessed through patient-reported measures such as the Western Ontario and McMaster Universities Arthritis Index (WOMAC), hip disability, and osteoarthritis outcome score (HOOS), EuroQol- 5 Dimension (EQ-5D), and 36-Item Short Form Survey (SF-36). The WOMAC primarily focuses on pain, symptoms, and daily activities in individuals with hip osteoarthritis, while the HOOS expands on this by including sub-scales for recreation and sports.^[5,6] The EQ-5D and SF-36 provide broader health assessments, with the SF-36 covering eight distinct sub-scales.^[7,8] Despite extensive research, no standard tool has been established to accurately predict post-operative outcomes for patients undergoing lower limb surgeries or rehabilitation outcomes following treating athletes with lower limb injuries.^[9,10]

The lower extremity functional scale (LEFS), developed by Binkley et al.. in 1999^[11] is extensively used to assess lower limb function. It is a straightforward, user-friendly tool designed according to a model proposed by the World Health Organization.^[12]

LEFS offers excellent test-retest reliability (R = 0.94) and greater sensitivity to change compared to the SF-36, particularly in total joint patients. These attributes make the LEFS exceptionally superior for precisely tracking recovery and effectively setting goals in physical therapy, as well as a more efficient and suitable tool for thoroughly assessing lower extremity musculoskeletal issues compared to other commonly used measures.^[11] This is precisely why LEFS is deliberately chosen over other tools.

The original LEFS, developed and published in English, was designed to evaluate the functional status and level of athletes with musculoskeletal disorders in the lower limbs. It comprises 20 questions, each offering 5 numeric response options from 0 to 4, leading to an overall score that ranges from 0 (poor) to 80 (excellent). The LEFS has demonstrated outstanding reliability and responsiveness.^[13-15] However, before a questionnaire can be employed in a different language, it is essential for it to be translated and culturally adapted to the specific country where it will be applied.^[16,17] It is worth noting that, in comparison to the SF-36, the LEFS has demonstrated to have exceptional psychometric properties. After its establishment, the LEFS was culturally adapted and translated from its original English version into various languages worldwide, including German,^[12] Italian,^[18] Dutch,^[19] Persian,^[20] Brazilian Portuguese,^[21] Greek,^[22] and Malaysian^[23]

In each of these adaptations, the LEFS has consistently maintained a strong psychometric profile, demonstrating excellent reliability and validity. This makes the LEFS a reliable and trustworthy instrument for evaluating lower limb function in patients with musculoskeletal dysfunction across different cultures and languages ensuring its efficacy in various clinical and research environments worldwide. Translating and adapting the LEFS into Sinhala can profoundly impact rehabilitation and clinical practice in Sri Lanka. It would make functional assessments more accessible and culturally relevant, improving patient understanding and communication with healthcare providers. This enhances the accuracy of assessments and the effectiveness of personalized treatment plans. Standardizing the LEFS in Sinhala would enable consistent, comparable data collection across the country, aiding in better patient outcome tracking and local research. Ultimately, it empowers healthcare providers, improves treatment outcomes, and contributes to developing culturally appropriate rehabilitation practices and policies in Sri Lanka.

This study aimed to translate the LEFS into Sinhala and validate it through various procedures, including construct validity applying exploratory factor analysis, convergent validity assessed by Pearson’s correlation coefficient, and criterion validity through the gold standard method. This research addresses several significant gaps. First, there is a lack of a validated scale in Sinhala, highlighting the necessity for its development. Second, the study sought to establish an appropriate cutoff point for Sri Lankan athletes by creating a Sinhala version of the LEFS that retains the excellent psychometric properties, reliability, and validity of the original form, thus ensuring its suitability for use with Sri Lankan athletes.

MATERIALS AND METHODS

The accepted method for translating and validating a questionnaire involved several steps: Translating the questionnaire, establishing linguistic and face validity, and assessing internal consistency through Cronbach’s alpha. Principal component analysis was conducted in this study to explore underlying factors, with factor analysis helping to understand how factor loadings correspond to meaningful themes, particularly in the newly translated questionnaire. For factor analysis, the sample size needed to include at least five participants per item in the questionnaire, as recommended by Mapi research trust guidelines. In addition, the specificity and sensitivity of the questionnaire were calculated.

This study was conducted as an observational study in two stages. Stage one began with the preliminary Sinhala translation and cross-cultural adaptation of the LEFS. In the second stage, a prospective evaluation of the critical psychometric properties of the Sinhala version of the LEFS was conducted.

The Ethics Review Committee of the University of Ruhuna granted the authorization for this study, and all participating athletes offered their written informed consent. In addition, the research and publication of the conclusions were granted by the copyright holder of the original LEFS.

Translation procedure

The LEFS was translated from its original English version to the Sinhalese version according to the forward/backward translation guidelines initially proposed by Guillemin et al.^[24] and later revised by Beaton et al [Figure 1].^[25]

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Figure 1:

Flowchart of the entire procedure of cross-cultural adaptation and validation of LEFS. LEFS: Lower extremity functional scale.

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Stage 1 consisted of the initial translation of the LEFS into Sinhalese and its cross-cultural adaptation

Step 1: Translation

Initially, two highly qualified health professionals, both native Sinhalese speakers with extensive expertise in medical terminology, methodically and independently translated the LEFS into Sinhala (T1 and T2, respectively). Both are esteemed medical professors at the Faculty of Medicine, bringing a wealth of knowledge and experience to the translation process. One of them is the distinguished authorized author of the validated Sinhala version of the 12-Item General Health Questionnaire (GHQ-12), while the other is the respected authorized author of the validated Sinhala version of the World Health Organization QOFBref (WHOQOL-Bref). Their collective expertise ensured a precise and culturally appropriate translation of the LEFS. Afterward, there was a combined conversation to combine and integrate the two respective unique forms as a unified and harmonized version. During this phase, the investigators’ prime exertions were dedicated to accomplishing conceptual and linguistic similarity with the original English editions.

Step 2: Back translation

This meticulous process was carried out by two authorized and officially registered Sri Lankan government translators in strict accordance with the by-laws outlined in the Sri Lankan government constitution. These translators, with their deep understanding of both linguistic nuances and legal requirements, ensured that the translation adhered precisely to the highest standards of accuracy and cultural sensitivity. Their authoritative expertise, combined with their comprehensive knowledge of the official regulations, played a crucial role in producing a translation that is both legally compliant and linguistically faithful to the original text.

This process was performed entirely to ensure that the translated version of the questionnaire was grammatically sound and the terms incorporated were precise and accurate. Similarly, the essential meaning and detailed contents of the inventive LEFS were meticulously well preserved.

The two forward and backward translations were carefully reconciled, with a thorough sentence-by-sentence revision. The accuracy of the translations was evident, as both English back translations were remarkably similar to the original English version.

In a subsequent detailed discussion, the same authors precisely reviewed and incorporated the necessary changes, leading to the finalized translated questionnaire. On concluding this comprehensive procedure, we achieved a combined and refined version of the Sinhala LEFS.

Stage 2 – involved a prospective assessment of the Sinhalese version of LEFS’s critical psychometric properties using the finalized Sinhalese version (S-LEFS)

• Step 01 – Selection of participants using inclusion and exclusion criteria

• Step 02 – Enrolment and administration

• Step 03 – Data collection and analysis.

RESULTS

The total number of participants was 146, and 34 of them refused to give written consent and did not fill out the questionnaires completely or satisfactorily. Consequently, a total of 112 questionnaires were carefully carried out once consent was granted. All 112 questionnaires were fully completed and then were incorporated into the subsequent evaluation and analyses. A total of 55 (49.11%) athletes were from the case group, and 57 (50.89%) athletes were from the control group. Athletes in the case group were identified as having lower extremity issues created by the hip, thigh, knee, leg, ankle, or foot. The Kaiser– Meyer–Olkin value found was 0.918, which was significant from a statistical standpoint (P < 0.0001). Equally, Bartlett’s Test of Sphericity had a significant value of P < 0.01. Accordingly, these detailed measurements clearly indicated the adequacy of the sample size used in this study.

Participants’ demographic data for each group is summarized in Table 1.

Construct validity

The construct validity of the S-LEFS was evaluated through EFA. The unforced analysis, utilizing Varimax rotation, discovered the extraction of three distinct components [Table 2]. On further analysis, the recognized pattern allowed us to classify these three components according to the intensity of the activities. These three factors accounted for 70.63% of the cumulative variance [Table 3, Figure 2]. Component one referred to high-intensity activity, Component two referred to moderate-intensity activity, and Component three referred to low-intensity activity. As indicated in Table 2, entire items counted factor loadings >0.48, and all items displayed excellent outcomes. Similarly, entire items exhibited exceptionally high factor loadings, and each item was explicitly assigned to its appropriate particular domains. Item 06 exhibited the minimal factor loading value (0.46). Even though it had the smallest value, it was still deemed satisfactory. Item 20, “Rolling over in bed,” was expected to score a high factor loading in the low-intensity domain, yet it surprisingly registered a greater value in the moderate-intensity domain.

Table 2: Factor loading of each item in the questionnaire.

Rotated component Matrixa
	Component
	1	2	3
Q1. Any of your usual work, housework, or school activities			0.767
Q2. Your usual hobbies, recreational or sporting activities			0.885
Q3. Getting into or out of the bath.		0.622	0.463
Q4. Walking between rooms.			0.759
Q5. Putting on your shoes or socks			0.739
Q6. Squatting	0.460	0.429	0.400
Q7. Lifting an object, like a bag of groceries, from the floor.		0.432	0.717
Q8. Performing light activities around your home.		0.561	0.467
Q9. Performing heavy activities around your home.		0.493	0.499
Q10. Getting into or out of a car.		0.786
Q11. Walking 2 blocks	0.466	0.721
Q12 Walking a mile.	0.751	0.419
Q13. Going up or down 10 stairs (about 1 flight of stairs)	0.597	0.631
Q14. Standing for 1 h.	0.702
Q15. Sitting for 1 h.	0.554	0.474
Q16. Running on even ground.	0.843
Q17. Running on uneven ground.	0.882
Q18. Making sharp turns while running fast.	0.859
Q19. Hopping.	0.841
Q20. Rolling over in bed.		0.462	0.403

Extraction method: Principal component analysis. Rotation method: Varimax with Kaiser normalization. ^aRotation converged in 6 iterations

Table 3: Principal component analysis of the LEFS in the sample (n=112).

Total variance explained
Component	Initial eigenvalues			Extraction sums of squared loadings
	Total	% of variance	Cumulative %	Total	% of variance	Cumulative %
1	10.745	53.727	53.727	10.745	53.727	53.727
2	2.056	10.282	64.009	2.056	10.282	64.009
3	1.326	6.629	70.638	1.326	6.629	70.638
4	0.900	4.500	75.138
5	0.699	3.493	78.631
6	0.549	2.747	81.379
7	0.523	2.615	83.993
8	0.482	2.409	86.402
9	0.436	2.181	88.584
10	0.358	1.791	90.375
11	0.307	1.537	91.912
12	0.297	1.485	93.397
13	0.237	1.187	94.584
14	0.210	1.050	95.634
15	0.185	0.926	96.560
16	0.166	0.832	97.393
17	0.156	0.781	98.174
18	0.143	0.717	98.891
19	0.126	0.629	99.520
20	0.096	0.480	100.000

Extraction method: Principal component analysis: The only Eigenvalue above 1.0 is mentioned. LEFS: Lower extremity functional scale

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Figure 2:

The scree plot of the principal component analysis.

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Criterion validity

With reference to criterion validity, an ROC curve was generated to compute the cutoff score of the LEFS. In this study, the scale was analyzed against clinical judgment as the gold standard. Athletes who did not have any lower extremity dysfunction or injury were considered normal participants in the study. Individuals who counted high total LEFS scores were thought to have optimal lower extremity function. With regard to this study, to clarify the sensitivity and specificity metrics, the following detailed analysis was performed. The area under the ROC curve for the LEFS was 0.938, indicating an exceptional ability of the scale to differentiate between athletes with and without lower extremity abnormalities. The ROC curve’s area under the curve (AUC) ranges from 0.5, representing no discrimination, to 1.0, representing perfect discrimination, with a value above 0.9 demonstrating outstanding performance. The study established a cutoff point of 67.5 for the LEFS score, chosen to balance sensitivity and specificity effectively. At this threshold, the LEFS exhibited a sensitivity of 87.5%, meaning it correctly identified 87.5% of athletes with lower extremity abnormalities as having a problem, thus showcasing high precision in detecting affected individuals. In addition, the scale achieved a specificity of 83%, indicating that 83% of athletes without lower extremity abnormalities were correctly classified as not having a problem, demonstrating its robust capacity to accurately classify those without the condition. Overall, these metrics were derived from comparing LEFS scores against a known diagnostic standard, with the high sensitivity reflecting the scale’s effectiveness in identifying abnormalities and the good specificity showing its ability to correctly identify non-affected athletes. The AUC of 0.938 further underscores the LEFS’s excellent performance in distinguishing between affected and non-affected athletes [Figure 3].

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Figure 3:

Receiver operating characteristic curve.

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DISCUSSION

It should be emphasized that, when assessing the health-related QOF, particularly in relation to the lower extremities, there is a prerequisite for an instrument to measure. Hence, this study is conducted to overcome this problem. As a self-report questionnaire, [Figure 4] LEFS offers us vital pertinency in both educational and clinical backgrounds. Hence, it is crucial to consistently employ a thoroughly validated and reliable health-related outcome measure. To be more specific, both culturally and linguistically appropriate adaptation might be obligatory to ensure it is a validated instrument. During the initial development of the LEFS, statistical analysis was applied to assess its reliability and validity. The findings were then compared to the SF-36 scores to determine the scale’s effectiveness. In this study, excellent results were obtained, though the methodology was different, with exceptionally high factor loading still achieved for all 20 items. To put it differently, it should be elaborated that entirely 20 questions included in the LEFS questionnaire are highly valid and reliably formulated questions to comprehensively assess various aspects of lower extremity function. The inventive author of the LEFS did not express it; however, this study managed to extract effectively three domains across the entire 20-item questionnaire. One of the domains appeared to comprise high-intensity activity (Questions 6, 12, 14, 15, 16, 17, 18, and 19), and the second seemed to involve moderate-intensity activity (Questions 3, 4, 5, 8, 10, 11, 13, and 20). Questions 1, 2, 7, and 9 were categorized as low-intensity activities; nevertheless, all scored a prominent factor loading of more than 0.4. The Cronbach’s alpha values in the original study of the LEFS development were remarkably high, measuring 0.96, and similarly, 0.952 in this study, both of which are outstanding. This emphasized the LEFS questionnaire’s exceptional ability to effectively distinguish between lower extremities with normal function and those experiencing issues, as demonstrated in both the original Binkley study and this research. Precisely speaking, one of the significant strengths of this present study was the exceptionally high measure of internal consistency, with a Cronbach’s alpha value of r = 0.952. This value is remarkably similar in comparison to other numerous cross-cultural adaptation studies that have translated the English version of the LEFS into various languages. Notably, in the Dutch version, the overall Cronbach’s alpha value for all 20 objects was an impressive 0.96. Similarly, an additional remarkable strong point of this research was its sufficiently large quantity of the sample, as evidenced by the statistically significant results of the Kaiser–Meyer–Olkin measure and Bartlett’s Test of Sphericity. These tests demonstrated a highly significant value, thereby demonstrating a substantial and reliable power of analysis.

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Figure 4:

Lower extremity functional scale original version English.

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In this present study, based on expert opinions, several key changes were thoughtfully implemented to ensure that the LEFS was culturally adapted across the entirety of Sri Lanka. Specifically, in adapting the LEFS from its English version to Sinhala, questions 3, 5, 10, 11, and 20 were slightly modified to better fit the context of the Sri Lankan population, ensuring the scale remains relevant and appropriate for local use.

• Bathing: The English version of Question 3 asks about “Getting into or out of the bath,” which was revised in the Sinhala version to simply “Bathing.” This change was necessary because bathtubs are not commonly used in Sri Lanka; most people bathe using showers or other methods.

• Footwear: Question 5 in the English version is “Putting on your shoes or socks.” In the Sinhala version, this was expanded to “Putting on your shoes, socks, or slippers” to reflect the common practice in Sri Lanka of wearing slippers in addition to or instead of shoes and socks.

• Transportation: The English version’s Question 10, “Getting into or out of a car,” was modified to “Getting into or out of a vehicle” in the Sinhala version. This adjustment acknowledges the widespread use of public transport and the variability in vehicle types used in Sri Lanka.

• Walking Distance: Question 12 in the English version refers to “Walking for 2 blocks.” This was adapted to “Walking for 150 m (500 steps)” in the Sinhala version because the concept of city blocks is not commonly used in Sri Lanka; instead, distances are typically measured in meters.

• Sleeping Surface: The English version’s Question 20, “Rolling over in bed,” was changed to “Rolling over in bed or on a mat” in the Sinhala version. This change accommodates the practice of sleeping on mats on the floor, which is common in many Sri Lankan households.

These modifications ensure that the Sinhala version of the LEFS [Figure 5] accurately reflects the daily life and cultural practices of the Sri Lankan population, improving the scale’s relevance and utility in assessing lower extremity function within this specific context.

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Figure 5:

Lower extremity functional scale Sinhala version (Cross culturally adapted and validated).

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In addition, Question 9 (Performing heavy activities around your home) should be categorized under component two (moderate-intensity activity) instead of component three. Similarly, Question 20 (rolling over in bed) should be classified under component three (low-intensity activity) instead of component two. It should be emphasized that these minor changes to the original version of the LEFS have been cross-culturally adapted into the Sinhala version of the LEFS, and it remains statistically highly reliable.

Furthermore, this study was precisely expanded to thoroughly test the psychometric properties of the S-LEFS, in contrast to the Sinhala language version of the WHOQOL-Bref, as many scholars regard this standardized comparison as essential. However, the correlation of the total score between S-LEFS and WHOQOL-Bref was insignificant since the WHOQOLBref has not been adequately questioned about the lower limb disability. Similarly, its other components, such as psychological, social, and environmental, were also not correlated significantly.

The S-LEFS offers several key benefits and applications in sports medicine in Sri Lanka. Initially, it provides a comprehensive baseline measurement of an athlete’s lower extremity function, establishing a clear understanding of the injury’s or condition’s impact on daily activities and sports performance. Regular administration of the S-LEFS allows for systematic tracking of recovery over time, enabling clinicians to objectively document improvements or setbacks and adjust treatment plans as needed. The detailed data from the S-LEFS facilitate the setting of realistic, specific rehabilitation goals tailored to individual needs, guiding the development of personalized rehabilitation programs. This tailored approach helps address specific functional deficits, prioritize interventions, and optimize the rehabilitation process for better athletic performance and outcomes. In addition, the S-LEFS is instrumental in evaluating the overall success of treatment interventions by comparing final outcomes with initial baselines, aiding in decisions about the athlete’s readiness to return to sport. It also enhances communication between athletes and health-care providers by providing clear, objective data on functional progress, helping athletes understand their recovery trajectory and stay engaged in their rehabilitation. Validating the S-LEFS for broader use across different regions and populations in Sri Lanka can significantly enhance its value in sports medicine. It will not only improve the consistency and quality of care provided to athletes but also contribute to a more standardized approach to assessing and managing lower extremity conditions. In summary, the S-LEFS is a powerful tool for sports medicine practitioners in Sri Lanka. Its use in routine assessments can help in setting precise treatment goals, monitoring progress, and tailoring rehabilitation programs, ultimately leading to more effective and personalized care for athletes with lower extremity conditions.

CONCLUSION

For the very first time, the original version of LEFS was successfully and precisely cross-culturally adapted into the Sinhala language. The psychometric properties of the S-LEFS have been reported to be exceptionally strong, especially with regard to internal consistency, reliability, and validity. This comprehensive adaptation makes the S-LEFS a highly reliable and valid tool for assessing lower limb function in Sinhala-speaking athletes who are experiencing musculoskeletal dysfunction in the lower extremities. Given its thorough validation, the S-LEFS can be confidently employed in both clinical and research settings to accurately evaluate and monitor lower limb functionality among this specific population.