Arabic Translation of the Knee Outcome Survey–Sports Activities Scale With Cross-cultural Adaptation and Validation

KOS-SAS Instrument

The KOS-SAS comprises 11 items that are subcategorized into 2 sections: the Symptoms subscale (7 items) and the Functional Limitations with Sports Activities (Functional Limitations) subscale (4 items) (Appendix Figure A1). The first 7 items evaluate knee symptoms in terms of severity, calibrated over 6 levels: “never have” (5 points), “have but does not affect sports activity” (4 points), “affects sports activity slightly” (3 points), “affects sports activity moderately” (2 points), “affects sports activity severely” (1 point), and “prevents me from all sports activity” (0 points). Items 8 to 11 assess the ability to perform specific knee athletic movements on a similar 6-level scale: “not difficult at all” (5 points), “minimally difficult” (4 points), “somewhat difficult” (3 points), “fairly difficult” (2 points), “very difficult” (1 point), and “unable to do” (0 points). ⁴ The final score is calculated by dividing the raw total score by 55 and multiplying the quotient by 100. The highest score (100) indicates normal knee function, while the lowest score (0) indicates the loss of knee function.

The KOS-SAS has 9 additional items that are not included in numerical scoring. These add-on items represent a complementary subjective assessment section for rating knee function during sports and the level and frequency of sports activities at different stages: before the injury, before treatment, and at the time of the survey response.

Translation and Cross-cultural Adaptation

We obtained written permission to translate the original English KOS-SAS from the primary author. ¹³ Conceptual rather than literal translations were implemented throughout the translation process. The KOS-SAS-Ar was developed in Modern Standard Arabic (MSA). The translation process was performed in accordance with the guidelines for cross-cultural adaptation of self-reported measures. ² First, 2 bilingual clinicians independently translated the original English version into Arabic. The translated version was then blindly converted back to English by 2 qualified translators from the College of Languages and Translation, King Saud University. Finally, we evaluated the quality of the final translation by comparing each Arabic-translated KOS-SAS item with its original English counterpart. The finalized KOS-SAS-Ar is available in Appendix Figure A2.

Patients and Study Design

The questionnaire was distributed to 276 patients with knee disorders. The participants were verbally invited and recruited from an orthopaedic clinic. The sampling method used was simple random sampling. After the exclusion of patients who did not fit inclusion criteria, participants were selected from a scheduled patient list of the outpatient orthopaedic sports clinic based on random numbers. The inclusion criteria were native Arabic speakers, patients with a history of sports injuries, and adults aged ≥18 years. The exclusion criteria were non-Arabic speakers, patients with degenerative abnormalities, patients with multiple joint injuries, and children.

The demographic data of the participants were collected, including their sex, age, height, weight, level of education, and duration of the knee condition. In addition to the KOS-SAS-Ar, the participants completed a visual analog scale (VAS) for pain ¹⁵ and the International Knee Documentation Committee (IKDC) subjective assessment of knee function. ^10,12 Help was available for the patients who required assistance in completing the questionnaire.

Validation and Reliability

Test-retest reliability refers to the degree of consistency of the test results over time. A reliable test should provide consistent measurements each time that the test is performed. In our study, we ensured test-retest reliability by administering the KOS-SAS-Ar to 20 patients from the study sample twice within a week. All participants of the retest stated that their knee conditions remained the same since the primary test. The standard error of measurement (SEM) indicates how far the measurements of a certain test are, relative to the true measurement. As the SEM increases, the test reliability decreases and vice versa. The smallest detectable change (SDC) refers to the minimum amount of change that is required to result in a real difference in the outcomes. Any change less than the SDC value can be attributed to a random error.

Internal consistency reflects the degree of homogeneity among items of an instrument that share a common target measurement. We measured internal consistency using the Cronbach alpha. The Cronbach alpha is an index of internal consistency used to measure how 2 groups of items are related as a unit. The Cronbach alpha is expressed on a scale from 0 to 1, with higher values representing higher degrees of internal consistency.

Convergent validity describes how close 2 constructs are in terms of measuring relatively similar entities. For this purpose, we examined the participants’ scores on the VAS and KOS-SAS-Ar Symptoms subscale for convergent validity in reference to symptoms. Similarly, the participants’ scores on the IKDC subjective form and KOS-SAS-Ar Functional Limitations subscale were tested for convergent validity concerning function. Construct validity shows the extent to which a construct is valid for testing the target concept. The construct validity of the KOS-SAS-Ar was tested using confirmatory factor analysis.

Statistical Analysis

The data were analyzed using SPSS (Version 24.0; IBM). Descriptive statistics (mean, standard deviation, frequency, and percentage) were used to define quantitative and categorical variables. The SEM was calculated from the standard deviation of a set of scores and the reliability coefficient using the formula SEM = S√1-r, where S is the standard deviation and r is the reliability coefficient of the measurement. The SDC was calculated based on the SEM and a given degree of confidence, for instance, 95% (SDC = SEM × 1.96√2). The intraclass correlation for internal consistency of the KOS-SAS-Ar was evaluated using the Cronbach alpha in which values were interpreted as excellent (≥0.9), good (<0.9 to ≥0.8), acceptable (<0.8 to ≥0.7), questionable (<0.7 to ≥0.6), poor (<0.6 to ≥0.5), or unacceptable (<0.5). Convergent validity was assessed using Pearson correlation analysis between the KOS-SAS-Ar Symptoms subscale items and VAS scores as well as between the KOS-SAS-Ar Functional Limitations subscale items and IKDC subjective scores.

Simple regression analysis was used to observe the linear relationship between the KOS-SAS-Ar subscores for symptoms and sports activities. The construct validity of the KOS-SAS-Ar was determined by performing confirmatory factor analysis. A correlation matrix, the Kaiser-Meyer-Olkin (KMO) test of sampling adequacy, and the Bartlett test of sphericity were used to obtain 11-item factorability. In factor analysis, the principal component method was used, and the proportion of variance was estimated through initial eigenvalues expressed by each of the factors. Varimax rotation was used to obtain rotated factors. A P value ≤.05 was used to indicate statistical significance.

Limitations

The main limitation of this study was the relative lack of validated sports-focused knee functional scoring systems in the Arabic language. There is a remarkable scarcity of validated Arabic PROMs, indicating an existing gap in the literature. The availability of corresponding Arabic knee function scales for athletes can provide more rational comparisons. However, certain elements of the KOS-SAS-Ar have been matched with corresponding elements from similar scales for the sake of correlation and validation processes. It could be a limitation that convergent validity for the symptoms-related items of the KOS-SAS-Ar was tested using the VAS only. A further potential limitation of this study was the difficulty of including many participants from various geographic locations where certain Arabic dialects are predominantly spoken. However, the widespread use of MSA makes it the best available medium for communication among Arabic speakers.