Self-Care Agency in Patients with Primary Osteoarthritis of the Knee: Scale Development

Abstract

Purpose: The aim of this study was to develop an instrument to assess self-care agency in patients with primary osteoarthritis of the knee.
Method: The participants consisted of 386 patients with osteoarthritis of the knee. Scale development involved several phases, including item development, reliability testing, criterion-related validity testing, and construct validity testing.
Results: Confirmatory factor analysis was conducted in order to assess the extent to which the Self-Care Agency in Patients with Knee Osteoarthritis Scale (SCAKOS) structure fit the present data. The fit indices were approximately satisfactory (GFI=0.927, AGFI=0.907, CFI=0.919, RMSEA=0.045). The SCAKOS comprises five factors with 20 items. All standardized coefficients in the model were moderate to high and all t-values were acceptable (p<0.01). The factors are as follows: “ability to acknowledge and understand the disease and its severity,” “ability to adhere to a treatment strategy,” “ability to modify daily life to reduce load on the knees,” “ability to proactively adopt information and methods useful for preventing disease exacerbation,” and “ability to seek effective support and apply it to improving quality of life.” Cronbach’s alpha for the total SCAKOS score was 0.813. The SCAKOS score was correlated significantly with SCAQ score and self-care one’s health score (p<0.01).
Conclusion: We developed the SCAKOS to measure self-care agency in patients with primary osteoarthritis of the knee. These findings suggest that the scale is suitable for model building, and can also be effectively used to assess self-care agency in patients with knee osteoarthritis, particularly those in Japan.