The instrument, called the Chinese Total Knee Arthroplasty Patient-reported Outcome Measurement, or CTP, belongs to a class of questionnaires known as patient-reported outcome measures, or PROMs. Instead of relying on clinicians to grade range of motion on an X-ray or flexion angle with a goniometer, PROMs ask patients directly about pain, function, mood, and quality of life. Proponents argue this approach captures the outcomes that matter most, improves communication between doctor and patient, and detects meaningful improvement that physician-scored measures can overlook. Yet the field has a persistent blind spot: most widely used knee PROMs, including the Oxford Knee Score, the new Knee Society Score, and the WOMAC index, were developed in Western populations and only later adapted for Chinese speakers, often with limited attention to whether the underlying activities and social situations are actually relevant to the people answering them.

The stakes are enormous. Symptomatic knee osteoarthritis affects roughly 14.6 percent of adults in China, and the number of total knee replacement procedures grew at an annual rate of 27.43 percent between 2012 and 2019. Despite this surge, between 10 and 20 percent of patients report dissatisfaction after surgery, a figure that suggests recovery is not simply a matter of a technically flawless implant. The research team’s earlier searches of PubMed, Embase, Scopus, and major Chinese databases found no previously validated, de novo, multidomain PROM built specifically for Chinese knee replacement patients — a gap the new study set out to fill.

The project unfolded in stages. In prior qualitative work, the investigators built an initial pool of 135 candidate items through patient interviews, concept elicitation with a multidisciplinary panel of 17 joint surgeons, orthopedic nurses, rehabilitation therapists, statisticians, and psychologists, two rounds of Delphi expert consultation, and cognitive debriefing with patients. That process produced a six-domain, 35-item preliminary questionnaire. The new study then put the instrument through quantitative refinement across three sequential, independent cohorts totaling 1,748 participants recruited between June 2023 and June 2024, with twelve-month follow-up completed by June 2025. No patient appeared in more than one cohort, a design choice that strengthens the validity of each analytic phase.

The item-reduction statistics tell a striking story about cultural fit. Questionnaires only work if the answers spread out; if nearly everyone gives the same response, the item carries almost no information. Three items asking about preoperative expectations showed ceiling concentrations of 94.7, 84.7, and 56.7 percent, meaning the vast majority of patients gave the top answer, and the entire expectations domain was dropped. A jogging item floored at 71.7 percent ceiling, while questions about embarrassment when others see the knee produced floor effects. At the same time, activities central to Chinese daily life — squatting, rising from low seating without armrests, mild field labour, climbing stairs in buildings without elevators, and community exercise such as Tai Chi or square dancing — loaded strongly onto the scale and stayed in. The result is a final 22-item clinical questionnaire with ten bilateral symptom items, eight function items, three quality-of-life items, and a single global satisfaction question.

For the formal psychometric testing, the team concentrated on a 16-item operated-knee core score covering symptoms, function, and quality of life, deliberately scoring only the replaced joint to avoid contamination from the other arthritic knee. The reliability figures were impressive. Cronbach’s alpha, a measure of internal consistency that reflects how coherently items hang together, reached 0.864 for the total core score, with subscale values between 0.809 and 0.942. When 150 participants filled out the questionnaire twice, two weeks apart and before any surgery, the intraclass correlation coefficient was 0.836, indicating that scores are stable over time rather than bouncing with mood or measurement noise.

Validity results were more nuanced. Exploratory factor analysis on a random half of the final cohort supported a clean three-factor structure matching Symptoms, Function, and Quality of Life, with all items loading above 0.40 and the three factors together explaining 72.2 percent of variance. But confirmatory factor analysis on the other half told a partially different story: absolute fit indices such as the SRMR (0.05), RMSEA (0.04), and the chi-square ratio (2.13) met prespecified thresholds, while the comparative fit index (0.92) and non-normed fit index (0.91) fell just short of the strict 0.95 criterion. The authors are candid about this, describing the structure as receiving partial rather than uniform support that requires independent replication — an unusually honest framing in a literature where fit indices are sometimes selectively reported.

The team also benchmarked the new measure against WOMAC, the most entrenched Western instrument. Convergent validity was strong where constructs genuinely overlap: the CTP function domain correlated with WOMAC function at r = 0.698, and CTP symptoms tracked WOMAC pain at r = 0.605, exactly the pattern expected if both instruments are measuring the same underlying phenomena. The weak correlation (r = 0.355) between CTP quality of life and WOMAC stiffness was not a failure but a confirmation that the two domains are conceptually distinct — stiffness is not a proxy for life satisfaction. Most importantly, in the responsiveness analysis, the CTP total score dropped from 33.52 at baseline to 21.81 one year after surgery, an effect size of 1.34 and a standardised response mean of 1.66, both comfortably in the large-effect range. WOMAC produced even larger standardised changes, but the authors caution that effect-size magnitude depends on an instrument’s content and score distribution and should not be read as a head-to-head superiority contest. What the CTP offers is complementary coverage of symptoms, psychosocial impact, and culturally salient activities that WOMAC simply does not ask about.

The study’s limitations are clearly acknowledged. All three hospitals were tertiary centres in western China, so the findings establish multicentre evidence within that region rather than nationwide generalisability; dialect, occupation, healthcare access, and community habits vary considerably across the country. No recognised Chinese gold-standard knee PROM existed, making criterion validity impossible to assess, and the quality-of-life domain still awaits validation against independent generic health or mental-health measures. Future work, the authors write, should test measurement invariance across diverse regions, establish anchor-based interpretability thresholds so that clinicians know what a given score change actually means, and evaluate whether the CTP adds predictive information beyond established instruments.

Even so, the implications reach well beyond orthopedics. Roughly half of the participants reported primary education or less, and nearly three-quarters relied on rural cooperative medical insurance — populations routinely underrepresented in instrument development. The CTP demonstrates that a psychometrically sound measure can be built from patient interviews upward, tested in more than 1,700 real patients across multiple centres, and refined with transparent statistical criteria rather than ad hoc judgment. It takes patients an average of under five minutes to complete. As knee replacement volumes continue their steep climb in China and across Asia’s aging societies, the study makes a forceful case that outcome measurement should be grounded in the lives patients actually lead — whether that means a walk around a Western suburb or a deep squat in a courtyard garden. The questionnaire does not replace WOMAC and its peers, but it may finally ask the right questions of the people answering them.

Subject of Research: Development and multicentre psychometric validation of a culturally tailored patient-reported outcome measure for Chinese total knee arthroplasty patients

Article Title: Quantitative refinement and multicentre psychometric validation of the Chinese total knee arthroplasty patient-reported outcome measure: a prospective cohort study with repeated measures

Article References: Xu, C., Chang, X., Ye, F., Wu, H., Chen, G., Zhang, R., Yao, S., Shang, L., & Ma, J. (2026). Quantitative refinement and multicentre psychometric validation of the Chinese total knee arthroplasty patient-reported outcome measure: a prospective cohort study with repeated measures. The Lancet Regional Health – Western Pacific, 74, Article 101989. https://doi.org/10.1016/j.lanwpc.2026.101989

Image Credits: AI Generated

DOI: 10.1016/j.lanwpc.2026.101989

Keywords: total knee arthroplasty, patient-reported outcome measures, psychometric validation, knee osteoarthritis, Cronbach's alpha, WOMAC, cross-cultural adaptation, responsiveness, factor analysis, China, orthopedic surgery, quality of life