Translation, cross-cultural adaptation and measurement properties of the Brazilian Portuguese version of the central aspects of pain in the knee in individuals with knee osteoarthritis

BACKGROUND: Osteoarthritis is the most common joint disease worldwide and the leading cause of disability related to joint conditions. There are few relevant musculoskeletal pain measures adapted to Brazilian Portuguese, and the Central Aspects of Pain in the Knee (CAP-Knee) is not yet available in this language version. OBJECTIVE: To cross-culturally adapt and evaluate the measurement properties of the Brazilian Portuguese version (Br) of the CAP-Knee. METHODS: This was a methodological study with two phases: (1) the CAP-Knee was translated and cross-culturally adapted into Brazilian Portuguese; (2) measurement properties were tested. Patients with knee osteoarthritis (n = 130) completed the CAP-Knee-Br, as well as pain and central sensitization measures. Structural validity was assessed using exploratory and confirmatory factor analyses. Furthermore, standard error of measurement, minimal detectable change, percentage of standard error of measurement error, floor and ceiling effects, McDonald's omega (internal consistency), and the intraclass correlation coefficient (test-retest reliability) were calculated. RESULTS: The CAP-Knee-Br showed cross-cultural equivalence with the original version. Exploratory and confirmatory factor analysis replicated the original one-dimensional structure with 8 items. We found positive correlations between the CAP-Knee-Br with pain and central sensitization measures. The standard error of measurement, the minimal detectable change, and the percentage of the standard error of measurement were all good. No floor or ceiling effects were observed. The CAP-Knee showed good reliability with adequate internal consistency (0.76 [95% CI: 0.69, 0.82]) and good test-retest stability (0.89 [95% CI: 0.84, 0.94]). CONCLUSION: The CAP-Knee-Br proved to be a valid and reliable instrument for assessing the central aspects of pain in Brazilian individuals with knee osteoarthritis.