Psychometric properties of the Turkish high-activity arthroplasty score in TKA patients

Abstract

Background

Total knee arthroplasty (TKA) has become increasingly common in younger and more active patients. However, conventional patient-reported outcome measures frequently demonstrate ceiling effects and fail to capture the high functional demands of this population. The High-Activity Arthroplasty Score (HAAS) was designed to assess advanced functions such as running, stair climbing, and demanding daily activities. This study aims to translate, culturally adapt, and validate the Turkish version of HAAS (T-HAAS) for patients undergoing total knee arthroplasty (TKA).

Methods

Following Beaton’s guidelines, the HAAS was translated, back-translated, and pilot tested. Reliability was assessed using Cronbach’s alpha, the intraclass correlation coefficient (ICC₂,₁) based on a 7-day test–retest interval, the standard error of measurement (SEM), and the minimal detectable change (MDC). Content validity was ensured through expert committee review and pilot testing. Construct validity was examined via convergent validity, using correlations between the T-HAAS and the Knee Injury and Osteoarthritis Outcome Score (KOOS), the Forgotten Joint Score–12 (FJS-12), the Numerical Pain Rating Scale (NPRS), and the Short Form Health Survey–36 (SF-36). Agreement was analyzed with Bland–Altman plots, and floor and ceiling effects were determined.

Results

Fifty-one patients with TKA (mean age 59.3 ± 5.4 years; 94.1% female) were included. The T-HAAS demonstrated excellent internal consistency (Cronbach’s α = 0.83) and excellent test–retest reliability (ICC₂,₁ = 0.96; 95% CI: 0.93–0.98). Measurement error indices were low (SEM = 0.55; MDC = 1.52), indicating high measurement precision and score stability. Exploratory factor analysis supported a single-factor structure of the T-HAAS, indicating sufficient one-dimensionality. Construct validity was supported in accordance with predefined hypotheses, with strong correlations observed for KOOS Pain (r = 0.65) and KOOS Sport (r = 0.61), and moderate correlations for the Forgotten Joint Score–12 (r = 0.52), KOOS Function (r = 0.50), and the NPRS (r = − 0.47) (all p < 0.001). Bland–Altman analysis demonstrated excellent agreement between repeated measurements, and no floor or ceiling effects were identified.

Conclusions

T-HAAS showed high reliability, strong construct validity, and no floor or ceiling effects in TKA patients.

Trial registration

ClinicalTrials.gov ID NCT05217264. Date of registration 18th January, 2022.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-026-09561-y.

Introduction

Osteoarthritis (OA) is a progressive degenerative disorder that imposes multifaceted challenges, including functional limitations, impaired proprioception, and muscle atrophy. By predominantly affecting weight-bearing joints such as the knees and hips, OA not only restricts mobility and range of motion but also markedly reduces quality of life and contributes to global disability and healthcare burden [1]. Advances in orthopedic surgical techniques over the past three decades have expanded the scope of total knee arthroplasty (TKA) to younger and more physically active individuals. Consequently, the proportion of patients under 65 years undergoing TKA has risen sharply and is projected to exceed 50% of all procedures by 2030 ^2,3. This demographic shift highlights the need for outcome measures that can capture higher levels of postoperative function in active patients.

As the number of TKA procedures continues to increase, reliably evaluating outcomes has become crucial for informing clinical decisions and providing optimal patient care. However, traditional assessment tools frequently demonstrate ceiling effects and fail to differentiate patients with higher functional demands, such as those engaging in recreational or sports activities [4]. As the proportion of younger and more active TKA recipients continues to increase, there remains a critical need for validated outcome measures capable of capturing high-level postoperative function [5, 6].

The High-Activity Arthroplasty Score (HAAS) was created to address these shortcomings and to evaluate higher-level functional abilities in younger, more active individuals undergoing TKA or total hip arthroplasty. In the HAAS literature, the term “younger” is used to describe patients with higher activity demands after arthroplasty and is commonly applied to populations younger than 65 years rather than implying a strict chronological definition. Originally published in English in 2010, the HAAS measures four areas: running, walking, overall activity level and stair climbing [4]. Cross-cultural adaptations in Italian, French, Dutch, and German populations have demonstrated strong validity, reliability, and minimal ceiling effects [7–10] underscoring the scale’s clinical utility across different contexts.

Currently, no patient-reported outcome tool specifically designed to assess high activity levels in Turkish-speaking individuals undergoing TKA has been encountered. Therefore, this study aimed to translate, culturally adapt, and validate the Turkish version of the High-Activity Arthroplasty Score (T-HAAS). We hypothesized that the T-HAAS would demonstrate adequate reliability and validity in this population. The availability of the T-HAAS will bridge an important gap by providing both clinicians and researchers with a robust tool for evaluating high-level function after TKA, thereby enhancing clinical practice, supporting research, and enabling cross-cultural comparability of outcomes.

Materials and methods

Study design and settings

This single-center methodological study conducted the translation, psychometric validation and cultural adaptation of the T-HAAS in individuals following primary TKA. It was conducted at the Orthopedics and Traumatology and the Physical Medicine and Rehabilitation clinics of Harran University Hospital. Ethical approval was granted by the Harran University Clinical Research Ethics Committee (HRU/21.12.21), and all procedures complied with the Declaration of Helsinki. The study was prospectively registered on ClinicalTrials.gov (c), and written informed consent was obtained from all participants prior to their enrollment.

Participants

We screened patients who had undergone primary cementless TKA for primary osteoarthritis at least six months previously and were followed at the Şanlıurfa Harran University Hospital. Inclusion criteria were age between 18 and 65 years, fluency in Turkish, and willingness to participate. Exclusion criteria were: revision surgery, prior lower-extremity operations, uncontrolled hypertension, and cognitive/learning impairments.

Translation and cross-cultural adaptation

The adaptation of the HAAS into Turkish followed the structured five-stage framework proposed by Beaton for cross-cultural adaptation of self-report instruments [11].

• I.Forward translation: Two native Turkish speakers independently translated the HAAS into Turkish—one a blinded academic researcher and the other an orthopedic surgeon with > 10 years of experience.
• II.Synthesis: A bilingual reviewer compared both versions and resolved discrepancies.
• III.Back-translation: Two independent translators produced English back-translations from the reconciled Turkish draft.
• IVExpert committee review: A panel of four translators and subject-matter experts compared the back-translated versions with the original instrument, resolving semantic or conceptual inconsistencies. This step resulted in the pre-final Turkish HAAS (T-HAAS).
• V.Pre-testing: The pre-final T-HAAS was pilot-tested in a sample of patients to confirm clarity, comprehensibility, and cultural relevance.

Preliminary testing

Cognitive debriefing interviews were conducted with 18 patients who had undergone TKA and met the eligibility criteria (10 females; mean age 49.4 ± 6.3 years). After completing the pre-final T-HAAS, participants were asked to report any difficulties in understanding the items and to provide suggestions for improvement. Feedback indicated minor issues in comprehension, which were addressed through item-level revisions. These modifications enhanced clarity and ensured cultural appropriateness of the instrument for Turkish-speaking patients. The revised version was subsequently finalized for psychometric evaluation.

Sample size

Sample size was determined according to the COSMIN study design criteria for patient-reported outcome measures. The COSMIN guidelines recommend a minimum of 50 participants for an ‘adequate’ rating in the evaluation of test–retest reliability, while a sample size of 100 or more is considered ‘very good’. In the present study, a total of 51 participants were included, which meets the COSMIN criteria for an adequate assessment of reliability. According to the COSMIN guidelines, a sample size of at least 50 participants is considered adequate for evaluating reliability, whereas a sample size of 100 or more is rated as very good [12].Therefore, the sample size of the present study can be considered adequate for the assessment of reliability.

Outcome measures

High activity arthroplasty score (HAAS)

The HAAS questionnaire includes four self-reported items that assess walking, running, stair climbing, and overall activity level. Each item provides response options ranging from normal ability to severe limitations, enabling patients to choose the highest level that reflects their functional capacity. Each response is scored, with higher values representing better function, and the overall score ranges from 0 to 18. Importantly, the original scale does not include guidelines for handling missing responses; therefore, all items must be completed to avoid incomplete data [4].

Knee injury and osteoarthritis outcome score (KOOS)

KOOS is a patient-reported scale designed to assess symptoms and eight functional states associated with knee injuries and OA. It consists of five subscales: pain, symptoms, activities of daily living, sports and recreational function, and knee-related quality of life. Paker et al. [13] conducted the Turkish validation and reliability study of the questionnaire. Each subtest of the scale is scored on a scale of 0 to 100, with patients providing responses based on their physical condition over the past week [14].

Forgotten joint Score-12

The Forgotten Joint Score-12 (FJS-12) is utilized to evaluate the extent to which individuals with TKA are able to disregard their artificial joints [15]. This scale assesses patients’ perceptions of artificial joint awareness during various daily activities, indicating their capacity to forget about the joint following surgery. Kınıklı et al. [16] carried out the Turkish validity and reliability study of the FJS-12, which includes 12 items. Responses are rated on a 5-point Likert scale (Never: 0, Almost never: 1, Rarely: 2, Sometimes: 3, Always: 4). The total score ranges from 0 to 100, with higher values indicating lower awareness of the artificial joint.

Numerical rating pain scale (NPRS)

A Numeric Pain Rating Scale (NPRS) typically includes a sequence of numbers accompanied by verbal descriptors, encompassing the entire spectrum of pain intensity. Patients are asked to rate their pain on a 0–10 scale, where 0 indicates “no pain” and 10 represents the highest level of pain imaginable often described as “the most intense pain possible,” “pain at its worst,” or “maximum pain.” [17].

SF-36

The Medical Outcomes Study Short Form Health Survey (SF-36) scale was employed to assess the overall health status of patients. SF-36 comprises 8 sub-domains and 36 items in total [18]. Each subscale is scored separately on a 0–100 range, where 0 reflects the lowest level of health and 100 represents the best possible health status. The Turkish validity and reliability study of this questionnaire was conducted by Koçyiğit et al. [19].

Statistical analysis

All statistical analyses were performed using SPSS software (Version 22.0; SPSS Inc., Chicago, IL, USA).

Structural validity of the T-HAAS was examined prior to internal consistency analyses using exploratory factor analysis. Principal axis factoring was applied to evaluate whether the empirical data supported the predefined structure of the original scale. Given the small number of items, a single-factor solution was forced and interpreted as a supportive analysis. No post-hoc model modifications or item reduction were performed. A one-factor confirmatory factor analysis (CFA) was also attempted to further examine the predefined structure of the scale; however, due to the very small number of items, the model was statistically under-identified and therefore not interpretable.

Internal consistency of the T-HAAS was examined using Cronbach’s alpha, which evaluates the degree of homogeneity among questionnaire items. Values between 0.70 and 0.95 were considered acceptable, whereas excessively high values may suggest item redundancy [15].

Test–retest reliability, reflecting the stability of the scale when administered at different time points under unchanged conditions, was assessed using intraclass correlation coefficients (ICC₂,₁). ICC values were interpreted as excellent (0.81–1.00), very good (0.61–0.80), good (0.41–0.60), fair (0.21–0.40), and poor (< 0.20) [20].

Construct validity of the T-HAAS was evaluated using hypothesis testing, in accordance with the COSMIN recommendations. Based on the theoretical construct of the HAAS as a measure of high-level physical function following total knee arthroplasty, the following a priori hypotheses were formulated:

Hypothesis 1

The T-HAAS would demonstrate moderate to strong positive correlations (r ≥ 0.50) with the KOOS Activities of Daily Living (ADL) and Sports/Recreation subscales, as these instruments assess closely related constructs of physical function and activity performance.

Hypothesis 2

The T-HAAS would show moderate positive correlations (r = 0.30–0.60) with the KOOS Pain, Symptoms, and Quality of Life subscales, given that these domains are related but not identical to high-level functional performance.

Hypothesis 3

A moderate positive correlation (r = 0.30–0.60) was expected between the T-HAAS and the Forgotten Joint Score–12 (FJS-12), as both instruments reflect functional integration of the joint during daily and recreational activities.

Hypothesis 4

The T-HAAS would exhibit a low to moderate negative correlation (r = 0.30–0.50) with pain intensity measured by the NPRS, because pain is related to, but does not fully represent, high-level functional ability.

Hypothesis 5

The T-HAAS was hypothesized to demonstrate moderate positive correlations (r = 0.30–0.60) with the physical domains of the SF-36 (Physical Functioning, Physical Role Functioning, and Bodily Pain), reflecting shared constructs of physical health and functional capacity.

Hypothesis 6

The T-HAAS would show weak or negligible correlations (r < 0.30) with the mental health–related domains of the SF-36, supporting discriminant validity.

Construct validity was regarded as sufficient provided that at least 75% of the expected correlations were supported by the data [21, 22].

Agreement between repeated measurements was further assessed using Bland–Altman plots. Floor and ceiling effects were considered to exist when more than 15% of participants obtained either the lowest or highest achievable score. Measurement error was quantified using the standard error of measurement (SEM), derived from the formula: SD*√1-ICC. The minimal detectable change at the 95% confidence level (MDC₉₅) was calculated using the formula: SEM × 1.96 × √2 [23].

Known-groups validity was evaluated by stratifying participants into tertiles of the KOOS total score (low, medium, and high function). Between-group differences in T-HAAS scores were analyzed using one-way ANOVA.

Result

Fifty-eight patients who had undergone TKA surgery were evaluated, and the trial was completed with 51 TKA patients after 7 patients were eliminated for not meeting the inclusion criteria. Table 1 presents the sociodemographic characteristics, clinical features, and baseline patient-reported outcome measures of the participants.

Table 1.

Sociodemographic, clinical, and patient-reported outcome characteristics of the participants

	Mean ± SD or n (%)
	59.27 ± 5.35
Age (years)
Body mass index (kg/m2)	30.9 ± 5.8
Sex
Male	3 (5,9%)
Female	48 (94,1%)
Civil status
Married	47 (92.2)
Widowed or divorced	4 (7.8)
Level of education
Primary school	46 (90.2%)
Secondary school	2 (3.9%)
High school	3 (5.9%)
KOOS
Symptoms	76.83 ± 6.95
Pain	76.06 ± 8.21
ADL	77 ± 7.85
Sport	31.86 ± 6.4
QoL	52.51 ± 12.67
FJS-12	57.58 ± 29.19
NPRS	2.49 ± 1.88
SF-36
Physical functioning	71.57 ± 16.2
Physical role functioning	63.24 ± 25.18
Bodily pain	74.31 ± 21.46
General health perceptions	52.35 ± 17.87
Vitality	54.78 ± 19.76
Social function	75.49 ± 17.49
Emotional role functioning	64.71 ± 39.68
Mental health	65.8 ± 17.35

Abbreviations: KOOS Knee injury, and osteoarthritis outcome score, FJS-12 Forgotten joint score-12, NPRS Numerical rating pain scale, SF-36 Short Form Health Survey-36

Translation, cross‑cultural adaptation, pre‑test phase

In line with the expert committee’s recommendations and the feedback from the pilot study, The Turkish version of the survey has undergone some modifications to be more easily understood by the patients and to make the survey culturally appropriate for Turkish people. All changes have been made in the 6th section titled “Activity Level”. The word recreational is translated into Turkish as “rekreasyon”. However, since this word is not used much in the Turkish population, it is not known what it means. For this reason, a description of “recreational activity” was added at the bottom of the questionnaire, defining it as “activities for leisure and/or sport”. In item 2, two more activities, “home/furniture painting” and “carpet/floor cleaning” was added. In item 3, one more activity, “table tennis” was added. In item 4, two more activities, “dancing” and “lightweight lifting” were added. Because of difficulty understanding, “high impact aerobics” in item 5, and “basketball” and “less than 10 minutes of running” were added. In item 6, one more activity, “football” was added. Changes and additions were made to HAAS by considering the metabolic expenditure value of each activity level and the regular activities in the daily lives of the Turkish population. After the changes, 12 volunteers (age: 46.2 ± 11.3; primary school graduate: 80%) reported that the questionnaire could be answered easily. The final version of Turkish HAAS (T-HAAS) is shown in Appendix-A.

Structural validity

Exploratory factor analysis supported a single-factor structure of the T-HAAS. All communalities exceeded 0.50, and the extracted factor explained 63.3% of the total variance. All four items loaded strongly on the factor, with loadings ranging from 0.71 to 0.86, supporting sufficient one-dimensionality.

Reliability

According to our assessment of the homogeneity of questions, the T-HAAS had excellent internal consistency (Cronbach alpha = 0,834). A second assessment was made one week later (7.9 ± 1.36 days). Test-retest reliability was excellent with ICC₂,₁ = 0.96 (95% CI: 0.93–0.98). In Table 2, we present the results of the reliability values of our analysis and comparisons with other translated versions.

Table 2.

Psychometric properties of the HAAS, including the Turkish version

	Cronbach’s Alpha	ICC (95% CI)	Time
English	0.86	n/a	n/a
French	0.58	n/a	n/a
German	0.75	0.96 (0.92–0.97)	2.4 min
Italian	0.91	0.95 (0.92–0.98)	1.6 min
Dutch	0.84	n/a	n/a
Turkish	0.83	0.96 (0.93–0.98)	1.9 min

Abbreviations: ICC Intraclass correlation coefficient, HAAS High Activity Arthroplasty Score

Agreement

The SEM for T-HAAS was 0.55 and MDC was 1.52 points. The agreement of T-HAAS is also shown using a Bland–Altman plot (Fig. 1).

Fig. 1.

Bland–Altman plot depicting the congruence of the T-HAAS

Construct validity

The T-HAAS demonstrated weak to strong correlations with all other patient-reported outcome measures. T-HAAS showed a strong correlation with the KOOS-pain (r = 0,649; p = 0,001) and KOOS-sport (r = 0,614; p = 0,001), moderate correlation with the FJS-12 (r = 0,517; p = 0,001), VAS (r=-0,472; p = 0,001), KOOS-symptom (r = 0,463; p = 0,001), KOOS-function (r = 0,503; p = 0,001). Correlation with the SF-36 subscales varied between weak (mental health, general health perceptions, social function, vitality, emotional role functioning) and moderate (physical role functioning, physical functioning, bodily pain). All predefined a priori hypotheses regarding construct validity were supported, with correlation coefficients observed in the expected direction and magnitude. In accordance with COSMIN recommendations, construct validity was therefore considered sufficient, as more than 75% of the predefined hypotheses were confirmed. Table 3 presents the correlations between the T-HAAS and the other assessment scales.

Table 3.

Correlations between HAAS and KOOS, FJS-12, NPRS, SF-36

	r (Correlation with T-HAAS)	p
KOOS
Symptoms	0.463	0.001
Pain	0.503	0.001
ADL	0.649	0.001
Sport	0.614	0.001
QoL	0.413	0.003
FJS-12	0.517	0.001
NPRS	0.472	0.001
SF-36
Physical functioning	0.506	0.001
Physical role functioning	0.496	0.001
Bodily pain	0.465	0.001
General health perceptions	0.254	0.073
Vitality	0.270	0.056
Social function	0.302	0.031
Emotional role functioning	0.266	0.059
Mental health	0.144	0.302

Abbreviations: T-HAAS Turkish version of high-activity arthroplasty score, KOOS Knee injury, and osteoarthritis outcome score, FJS-12 Forgotten joint score-12, NPRS Numerical rating pain scale, SF-36 Short Form Health Survey-36, ADL Activities of daily living, QoL Quality of life

Known-groups validity

When participants were stratified into tertiles based on KOOS total scores, T-HAAS values differed significantly across groups. Patients in the high-function KOOS group demonstrated the highest T-HAAS scores (11.1 ± 1.9), followed by the medium group (9.1 ± 2.3) and the low-function group (7.8 ± 3.3). One-way ANOVA confirmed a significant between-group difference (F [2,48] = 7.07, p = 0.002), thereby supporting the known-groups validity of the T-HAAS.

Floor and ceiling effects

Due to no patient not achieving either the minimum or maximum score, the T-HAAS did not indicate any floor or ceiling effects. Regarding the MDC, 11.76% of patients (n = 6) obtained a cumulative score between the greatest value and the MDC (12.48–14 points), but no patient did so for the MDC (0–1.52 points).

Discussion

This study aimed to evaluate the reliability and validity of the HAAS among Turkish-speaking patients who underwent total knee arthroplasty. The findings of the present study demonstrated that the T-HAAS exhibits sufficient one-dimensionality, acceptable internal consistency, excellent test–retest reliability, and adequate construct validity, without evidence of floor or ceiling effects. Collectively, these results indicate that the T-HAAS is a reliable and valid single-score instrument in patients following TKA.

The T-HAAS proved to be a brief and feasible instrument, with an average completion time of 1.9 min. No difficulties were reported during administration, confirming its clarity and comprehensibility after the expert committee revisions and pilot testing. Previous studies have highlighted the limitation of the “activity level” item in the original HAAS due to cultural specificity of recreational activities [4]. In our adaptation, this weakness was mitigated by incorporating metabolic equivalent activities relevant to daily life in Turkey, thereby enhancing cultural appropriateness. In addition, the Italian [7] and German versions of the scale [10], which measure the completion time, have reported times similar to ours (1.6 min, and 2.4 min, respectively). In the German version, the questionnaire was completed online. The patient started answering after logging in and logged out after finishing. However, we think that the completion time is longer since it is not known that the patients log out right after they finished.

The T-HAAS demonstrated excellent internal consistency (Cronbach’s α = 0.83) and test–retest reliability (ICC = 0.96). These findings are consistent with those reported for the original English, Italian, and German versions and are superior to the French and Dutch adaptations [7–10]. In particular, the test–retest reliability of the Turkish version (ICC = 0.96) is comparable to that of the German (ICC = 0.96) and Italian (ICC = 0.91) versions. As ICC values were not reported for the Dutch, French, or original English versions, direct comparisons with these adaptations were not possible.

Since ICC values are not directly interpretable in clinical practice, complementary indices such as SEM and MDC are recommended to evaluate absolute reliability. The MDC represents the smallest detectable change that reflects a true clinical difference rather than measurement error. In practical terms, if functional activity scores do not improve beyond the MDC, clinicians may consider alternative treatment strategies. To date, SEM and MDC values for the HAAS have rarely been reported, with the German version being the only exception (SEM = 0.54; MDC = 1.5) ¹⁰ Our findings for the T-HAAS were nearly identical (SEM = 0.55; MDC = 1.52), indicating that score changes greater than 1.5 points can be interpreted as clinically meaningful in Turkish TKA patients.

Construct validity of the T-HAAS was supported by its correlations with other patient-reported outcomes. Strong associations were observed with KOOS-pain and KOOS-sport, as well as moderate correlations with the FJS-12 and NPRS. In addition, the T-HAAS correlated moderately with the physical functioning, role-physical, and bodily pain subscales of the SF-36, while associations with general health, social functioning, role-emotional, mental health, and vitality were weak.

Moreover, the T-HAAS showed moderate correlations with the SF-36 subscales for role-physical, physical functioning, and bodily pain, whereas its associations with general health, mental health, role-emotional, vitality and social functioning, were weak. These results confirm that the T-HAAS predominantly reflects physical aspects of health, rather than psychosocial domains. Comparable findings were reported in the German and Dutch versions, which also showed moderate to strong correlations with KOOS and FJS-12, and in the Italian version, where correlations with SF-36 mental health components were similarly low [9, 10]. Furthermore, the significant differences in T-HAAS scores across KOOS tertiles support the discriminative validity of the instrument, consistent with its intended purpose of distinguishing patients across functional levels.

None of the patients obtained the lowest or highest possible T-HAAS scores, indicating the absence of floor and ceiling effects. This finding, consistent with other language adaptations and previous reports [24], confirms the ability of the HAAS to discriminate effectively across a wide spectrum of functional outcomes in TKA patients.

In clinical practice, these findings suggest that the T-HAAS can serve as a brief, feasible, and reliable tool for monitoring high-level functional abilities in Turkish-speaking TKA patients. Its ease of administration and discriminative capacity make it suitable for both routine follow-up and research settings.

This study has several limitations. First, responsiveness, defined as the ability of a tool to detect clinically meaningful changes over time, was not assessed in the present study. As this study was cross-sectional in design, future longitudinal studies are warranted to evaluate the responsiveness of the T-HAAS. Second, the single-center design and the fact that all surgeries were performed by one surgeon may restrict generalizability. Another limitation of this study is the predominance of female participants, which may limit the generalizability of the findings to male patients undergoing total knee arthroplasty. Although the primary aim of this study was to evaluate the psychometric properties of the T-HAAS rather than to compare clinical outcomes between sexes, the observed gender imbalance has been explicitly acknowledged. Future studies with more sex-balanced samples are warranted to further confirm the applicability of the T-HAAS across different patient populations. These factors should be considered when interpreting the findings, and future research in larger, more diverse, and multicenter cohorts is recommended.

Future research should examine the responsiveness of the T-HAAS and establish minimal clinically important difference (MCID) values to enhance interpretability. Large-scale, multicenter studies with more balanced sex distributions are also warranted to further support generalizability.

Conclusion

The T-HAAS demonstrated excellent reliability, low measurement error, strong construct validity, an absence of floor or ceiling effects in patients after total knee arthroplasty. In addition, known-groups validity confirmed its discriminative capacity across different functional levels. These results suggest that the T-HAAS serves as a concise, practical, and reliable instrument for evaluating advanced physical functioning in Turkish-speaking TKA patients. Future studies should examine its responsiveness and establish minimal clinically important difference values to further enhance its clinical applicability.

Authors’ contributions

All authors declare to have no conflict of interest.

Funding

This work was supported by the Research Fund of the Inonu University. Project Number: TSA-2025-4279.

Data availability

The datasets generated and/or analyzed during the current study are not publicly available due to participant privacy regulations but are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

Ethical approval was received from the Harran University Clinical Research Ethics Committee (HRU/21.12.21) All participants provided written informed consent before participation. The study was conducted in accordance with the principles of the Declaration of Helsinki

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.