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 Table of Contents  
Year : 2020  |  Volume : 15  |  Issue : 3  |  Page : 201-206

Determinants of self-care behaviors in patients with knee osteoarthritis based on the theory of planned behavior in Iran

1 Department of Health Education and Promotion, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
2 Department of Department of Health, Faculty of Medical Sciences, Shahrekord Branch, Islamic Azad University, Shahrekord, Iran
3 Department of Rheumatology, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
4 Department of Biostatistics, Research Center of Prevention and Epidemiology of Non-Communicable Disease, Shahid Sadoughi University of Medical Sciences, Yazd, Iran

Date of Web Publication3-Sep-2020

Correspondence Address:
Dr. Sakineh Gerayllo
School of Health, Shahid Sadoughi University of Medical Sciences, Yazd
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/injr.injr_150_19

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Introduction: Knee osteoarthritis (OA) is one of the most prevailing causes of knee joint pains depending on age and one of the main reasons for functional deficiency. As patients are in need of effective self-care plans in promoting health, so that, this study was conducted with an aim to study the determinants of self-care behaviors in the patients with knee OA referring to clinical centers of Yazd city based on theory of planned behavior (TPB).
Methods: The cross-sectional study was performed on 235 patients who referred to the health-care centers of Yazd city. A questionnaire was developed and used to collect the data based on TPB constructs. Data were analyzed using SPSS 18 software and by the statistical tests of correlative coefficient, Chi-square, and linear regression at 0.05 significance level.
Results: This study was conducted on 235 patients. Based on the results of Pearson correlation test, the self-care behaviors of knee OA had a statistically significant positive correlation with all constructs of the TPB (P < 0.05). Following data analysis, the constructs of the TPB predicted 8% of the variance of intention and 16.2% of the variance of OA self-care behaviors.
Conclusion: According to the results, the TPB can be suitable for explaining knee OA self-care behavior. Furthermore, recurrent training can be effective in promoting behavioral intention of patients in self-care.

Keywords: Behavior intention, knee osteoarthritis, self-care, theory of planned behavior

How to cite this article:
Morowatisharifabad MA, Gerayllo S, Karimiankakolaki Z, Dehghan A, Salehabadi HS, Fallahzadeh H. Determinants of self-care behaviors in patients with knee osteoarthritis based on the theory of planned behavior in Iran. Indian J Rheumatol 2020;15:201-6

How to cite this URL:
Morowatisharifabad MA, Gerayllo S, Karimiankakolaki Z, Dehghan A, Salehabadi HS, Fallahzadeh H. Determinants of self-care behaviors in patients with knee osteoarthritis based on the theory of planned behavior in Iran. Indian J Rheumatol [serial online] 2020 [cited 2021 Jun 18];15:201-6. Available from:

  Introduction Top

Osteoarthritis (OA) is a chronic progressive disease of the articular cartilage and subchondral bone.[1] The increase of global load of these diseases has made the UN(led by WHO) term the first decade of the 21st century as the decade of bone and joint diseases through 2000–2010.[2] OA is one of the most common chronic diseases[3] and limiting element of activities among old people in developed countries,[4] and it is the main source of morbidity, inability, or losing the function among people.[5] The economic effect of vascular skeleton disorders of OA has been estimated to be as equal as the outcomes of cancer.[6] OA is the most common form of arthritis which is associated with the progressing decay or gradual loose of joint cartilage[7],[8] and finally leads to joint destruction.[9] The prevalence of OA is increasing nowadays.[3] It is expected that this trend should be continued with regard to the oldness of the population and increase of fatness.[5],[10],[11],[12] At present, more than 20 million American people are afflicted with OA.[13] Among the body joints, knee is the most prevailing place of affliction with disease.[14] The knees are among the joints most commonly affected by OA[15] and compared with other joints, and it makes more disability and shows more clinical symptoms. According to the existing evidences, in the whole world, it is one of the most common causes of disability.[11] Many people who are suffering from knee OA are complaining of pain, stiffness and vascular weakness, and limitation in walking.[16],[17] Knee OA is a multifactorial disease that is affected by mechanical factors.[18] Age is one of the strongest risk factors in OA, and the prevalence of OA is increasing as the population ages.[19] It is such that its prevalence is from 4% in 18–24 years old to 85% in 75–79 years old.[7] This disease is more common in women as compared with men.[20]

In Iran, according to the Community Oriented Program for Control of Rheumatic Diseases study, the rate of affliction and damages of OA prevalence in knee joint is 15.3% in the urban society and 19.3% in rural society which is much higher than other Asian countries.[21] With regard to different reasons such as cultural reasons (the culture of sitting on the earth and carpet), apartment way of life and low activity, it can be said that the most common type of OA is in Iran.[21],[22] Self-care is an effective factor to help with the patients gain individual independence and increase health related quality of life.[3] The important principle in self-care is participation and acceptance of responsibility by the patient, so that by performing correct behaviors related to it, many damaging consequences of the disease could be controlled.[23] A noticeable rate of behavioral theories and different models has been used to study the health behaviors.[24]

The theory of planned behavior (TPB) is a social cognition model which forms an optimistic framework to understand and predict the behavioral intention and behavior.[25] Based on TPB assumptions, when individual will be motivated to do health behaviors (knee OA self-care) and even in facing challenges, they feel have control over the respective behavior and can manage it.[26] In the TPB, behavioral intention is the most significant predictor of behavior.[24] The intention is determined under the influence of attitude toward behavior, subjective norms, and perceived behavioral control (Ajzen, 1980).[26] Attitude is determined by the individual beliefs on results or the specific features of behavior performance (behavioral beliefs). Similarly, subjective norm of a person through his/her own normative beliefs determines whether or not the important persons confirm or reject his/her behavior. The perceived behavioral control on the presence or lack of facilitators or obstacles of behavioral performance or the effect of each of the controlling factors is to facilitate or control a behavior.[24] As a general rule, the more favorable the attitude and subjective norm, and the greater the perceived control, the stronger should be the person's intention to perform the behavior in question.[24] The design of the TPB model is presented in [Figure 1].
Figure 1: Theory of planned behavior

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As knee OA is the most common diseases of skeleton system in human which can cause disability and inability and can be associated with different socioeconomic consequences and it is also the source of resultant such as obesity, age increase, race, hormone, and job issues and also due to the most common culture and behaviors such as sitting on the ground, using the squat toilet in particular among the aged, and with regard to the fact that so far the TPB has not been used to explain arthritis self-care, the present study was conducted in order to study the self-care determinants in the patients with knee OA referring to the clinical centers in Yazd city based on the TPB.

  Methods Top

This was a descriptive-analytic and cross-sectional study which was conducted. The necessary sample size with the consideration of confidence level of 95% and with regard to the quantity of S (maximum rate of standard deviation of self-care behavior score in the pilot study) and estimation error of 2 units was estimated to be as equal as 235 patients.


Compatible with the present study, they have shown that when there is a stronger relation between intention and behavior, the concerned behavior will be performed with a greater possibility. Those who were an inhabitant of Yazd Province had a primary OA diagnosed by a rheumatology specialist, had an age below 70 years, and signed the informed consent form to take part in the study were eligible to participate in the study.

Data collection procedures

The tools to collect data were a researcher-designed questionnaire containing two parts. The first part of the questions was related to demographic data. The second part was related to the constructs of the TPB including 11 questions of behavioral intention, 11 questions of attitude, 22 questions of subjective norms, 24 questions of perceived behavioral control, and finally, 12 behavior questions. In this study, in order to respond to the questions of all constructs, a 5-point Likert scale was employed and each of the questions was given a 1–5 score.

The face validity of the scales was approved by a panel of experts, and the internal consistency of the scale was measured in a pilot study by 35 eligible participants. The sample subscales TPB questionnaire and the Cronbach's alpha calculated are shown in [Table 1].
Table 1: Sample subscales theory of planned behavior questionnaire and the Cronbach's alpha calculated items

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One of the researchers used to be present concurrent with the time where the specialist was in the related centers in the morning and evening shifts. The patients were being selected randomly and voluntarily, and the questionnaires were being completed in the form of conducting an interview with the patients.

Statistical methods

The collected data were analyzed using SPSS software version version 18.0 (SPSS Inc., Chicago, IL, USA) and due to the normality of the data using the Kolmogorov–Smirnov test of statistical tests, correlative coefficient, Chi-square, and linear regression at 0.05 significance level.

Ethics approval and consent to participate

In order to participate, all participants gave written informed consent, and ethical approval for this study has been obtained by the Ethics Committee affiliated with Shahid Sadoughi University of Medical Sciences, Yazd, Iran.

  Results Top

Of the total 235 patients participating in this research, 218 (92.8%) were women and 17 (7.2%) were men in which the age average of women was 54.68 ± 9.04 and that of men was 57.73 ± 10.55 years. The average body mass index in women was 28.80 ± 4.62 and in men was 28.62 ± 4.62. One hundred and eighty-eight (80%) participants were married and 211 people (89.8%) were urban settler. The findings showed that most of them were illiterate (106 people 45.1%) and only 21 people (8.9%) were with academic education. The greatest rate of the job frequency was in the housewife group with the frequency of 173 people (73.6%). The greatest rate of individuals under consideration was 141 people (60%) who reported their economic standard as equal to average [Table 2].
Table 2: Frequency distribution of demographic characteristics of patients

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Based on the results of Pearson correlation test, the self-care behaviors of knee OA had a statistically significant positive correlation with all constructs of the TPB. The correlation matrix of all constructs is shown in [Table 3].
Table 3: Means, standard deviations, and partial correlations (Pearson's r) among the study constructs

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The attitude, subjective norms, and perceived behavioral control predicted 8% of the variance of knee OA self-care behavior intention of which the attitude was the strongest predictor (β = 0.214) [Table 4].
Table 4: Linear regression of behaviors intention and knee osteoarthritis self-care behaviors on attitude, subjective norm, and perceived behavioral control

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The constructs of the TPB including attitude, subjective norms, and perceived behavioral control have predicted 16.2% of the variance of knee OA self-care behaviors, and among the structure, the most powerful predictor was perceived behavioral control (β = 0.363) [Table 4].

  Discussion Top

This study which was conducted with the aim of determining knee OA self-care behavior predictors and the quality of determining these behaviors by the constructs of the TPB was specified.

In the present study, from the viewpoint of correlation among the constructs, there was the strongest relation between intention and self-care. Intention is the stage before action, and during this stage, an individual is ready to perform a behavior, but this intention is not always leading to a behavior, because different factors are leading to some changes in an individual's intention to do a behavior. In the next rank, there is the perceived behavior control which has a greater correlation with self-care behavior. In fact, if an individual feels that he/she can overcome the external factors affecting the self-care behaviors, he/she will face its problems much easier.

In this study, there is a positive significant relation between the intention and self-care behavior by the patient which is under the influence of their attitude including the positive and negative beliefs toward the behavior.

The findings of this research indicate that intention and self-care behaviors had a statistically positive and significant correlation. The presence of positive correlation indicates that to the extent that the intention of an individual to do a self-care behavior higher while following a behavior, to the same extent, he/she will do a greater self-care behavior. Ajzen and Fishbein also have expressed that the intention predicts the real behavior and it is the formation of intention which can lead to a behavior.[27]

There is a correlation between subjective norms and self-care intention in the patients. These results are compatible with the results of the studies by Omondi et al.,[28] also Blue,[29] and Arvola et al.[30] However, a study by Bozionelos and Bennett on predicting the behavior of sports based on the TPB showed that the construct of subjective norms does not have a significant relation with the intention.[31] Furthermore, there is a direct relation between subjective norms and behavioral control and intention which is compatible with the study made by Arvola et al.[30]

The constructs of the theory predicted 8% of the variance of the intention of knee OA self-care behavioral intention in which among the constructs, the attitude was the strongest predictor. This attitude is vital in motivating the individual and creating incentive to adopt a self-care behavior. The educational programs should focus a part of their activities on promoting the peoples' attitude and based on change in individual's attitude through the application of effective methods to provide the necessary incentive for self-care behaviors.

However, in a study, Abamecha et al. made a HIV volunteer consultation and voluntary counseling and testing test.[25] Furthermore, Molla et al. studied the intention of self-report on using condoms among rural women in Ethiopia.[32] They showed that the predicting subjective norms were stronger than intention which is in conflict with the results of this study.

Attitude, subjective norms, and perceived behavioral control have been able to predict 16.2% of the variance of self-care behaviors in respect to knee OA. Hence, it can be concluded that the TPB can serve as a reference framework to design the educational programs among these patients. It was also specified that the perceived behavioral control is the strongest predictor for knee arthritis self-care behavior.

The results of the study showed that the construct of predicting subjective norms is not significant for intention and behavior. This result indicates that when the population under consideration express that the others who are important to them do most of their self-care behaviors, they consider their beliefs as values and conduct self-care behaviors. In this case, the reference groups can have an impact on individuals' behaviors and make them familiar with the methods of lifestyle and influence individuals' attitudes and way of thinking and finally act as the confirming sources of a behavior. These findings of the present study are incompatible with the studies Omondi et al.[28] and Blue[29] who have studied the determining factors of intention to perform a physical activity and found that the subjective norm was the strong predictor of intention. The reason for the contradictory results of the study on the structure of subjective norms should be sought in the different nature of behaviors under consideration and the respective individuals' cultural, social, and personal characteristics [Table 5].
Table 5: Summarizing the findings from other studies on planned behavior

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The limitation of the study was individuals' self-reporting that could be detrimental to the study results. Although it was tried to reduce the deficiencies with a full description of the research issue, it is recommended to examine the participants' behavior by observation and trial or ask them to register their self-care behaviors throughout the day in future studies. Due to the nature of this study which is a cross-sectional study, this feature limits the generalization of the results. In order to achieve a more complete and precise results, it is suggested to perform this study in a broader level.

  Conclusion Top

Based on the results of the research, it can be said the use of the TPB as a planned framework for self-care in patients with knee arthritis is suitable. However, in general, with regard to the complex nature of health behaviors, no theory or model can describe or predict all aspects of health behaviors solely. In order to have an effect on a behavior, the combination of coordinated and compatible theories and models can act concurrently, and in fact, in compliance with behavioral needs and features, they can create a much stronger health education interventions.


The authors would like to appreciate the sincere cooperation of the Dean of the School of Health and also the patients who took part in this study.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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  [Figure 1]

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]


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