Introduction

Degenerative Joint Diseases (DJD) represent one of the most prevalent diseases impacting individuals worldwide1. In 2019, approximately 528 million people worldwide were living with osteoarthritis (OA), representing an increase of 113% since 1990. Approximately 73% of people living with osteoarthritis are older than 55 years, and 60% are female2,3. With a prevalence of 365 million, the knee is the most frequently affected joint, followed by the hip and the hand3,4. Females demonstrate a greater risk for the development of knee OA5, being affected at nearly twice the rate of males6. Women typically have less cartilage and experience greater cartilage volume loss5,7. Both knee laxity and OA symptoms are more severe in females compared to males5,8,9,10. Furthermore, women experience decreased estrogen levels during the postmenopausal period5,11,12. The estimated lifetime risk of knee OA for people with obesity is 24% for females and 16% for males5,13. Yoshimura et al.14 identified a higher prevalence of knee osteoarthritis in women compared to men, suggesting a potential sex disparity in the disease.

Osteoarthritis prevention and treatment can potentially mitigate both its onset and the severity of associated symptoms, which can be achieved through lifestyle modifications, early intervention for genu varum deformity (prior to the manifestation of arthritis), and weight reduction in obese individuals1. Therefore, adopting a healthy and appropriate lifestyle may contribute to lowering the prevalence of osteoarthritis, its complications, and the resultant challenges15. Research by Messier et al. (2021) demonstrated that older adults with knee OA who completed 1.5-year Diet or Diet + Exercise interventions experienced partial weight regain 3.5 years later; however, relative to baseline, they maintained statistically significant changes in weight loss and reductions in knee pain16. A study by Kaddah et al. (2023) revealed that the treatment of proximal tibia vara using high tibial osteotomy (HTO) with a dynamic axial fixator (DAF) in adolescents and young adults proved safe and effective17. Additionally, Preece et al. developed an intervention with five components for knee osteoarthritis (2021): making sense of pain, general relaxation, postural deconstruction, responding differently to pain, and functional muscle retraining, which they termed Cognitive Muscular Therapy. Their preliminary feedback and clinical indications were positive18.

Health experts emphasize lifestyle modification as a cornerstone of treatment, advocating for the adoption of healthy behaviors and the modification of detrimental ones for long-term benefits19. The Theory of Planned Behavior continues to provide a useful framework for research in the social20, health21, and behavioral sciences. The studies reported in these special issues illustrate the ongoing interest in using the TPB to explain and predict behavior in various domains. Furthermore, they demonstrate that the theory is a work in progress, as investigators continue to explore the intricacies of the structural model, such as the moderating effects of perceived behavioral control, and propose additional factors to account for the complexity of human behavior20.

Given the importance of osteoarthritis prevention in vulnerable populations, particularly women, this study aimed to design and implement an educational intervention based on the TPB to promote preventive behaviors for knee osteoarthritis among women aged over 40 residing in Fasa, Fars province, Iran. The research question addressed in this study was: What is the impact of an educational intervention based on the TPB model on preventive behaviors for knee osteoarthritis among women aged over 40 residing in Fasa, Fars province, Iran?

Materials and methods

Study design

This research employed a quasi-experimental design that was conducted in 2019. The study sample comprised 100 women aged over 40, all of whom were registered with the Fasa Health Centers in Iran. Two centers were randomly selected from the six available; one served as the control group, and the other was designated as the experimental group. Within each center, 50 subjects were selected using a simple sampling method based on their family file numbers in the computer records (50 per group). The sample size of 100 participants was determined to achieve a significance level of 5% (Type I error) and a power of 95%, while anticipating a 20% mean difference between groups.

The inclusion criteria were: (a) being female and over 40 years old and (b) being literate. The sole exclusion criterion was a pre-existing diagnosis of knee osteoarthritis. Participation in the study was voluntary, and all participants were assured that their data would remain strictly confidential. Both groups then completed the assigned questionnaires.

After participant selection, the intervention commenced with the experimental group. The intervention program consisted of eight training sessions designed to promote the adoption of preventive behaviors for knee osteoarthritis, based on the principles of the Theory of Planned Behavior (TPB). The behaviors of interest (maintaining a proper diet, achieving proper and sufficient sleep, learning how to sit, walk, stand, and sleep, maintaining weight control, performing exercise according to expert opinion, and understanding the amount and proper execution of these activities) were clearly defined in terms of their target, action, context, and time elements based on Fishbein and Ajzen’s (2010) perspective22. The program employed a multifaceted approach, incorporating lectures, group discussions, role-playing activities, video presentations, and PowerPoint slides. To further enhance engagement, two of the training sessions included workshops led by an orthopedist and physiotherapist, during which participants could be accompanied by a family member. Each participant in the experimental group received an instructional booklet upon completion of the training sessions. Additionally, two follow-up sessions were held at monthly intervals, and weekly text message reminders were sent to participants. To assess the impact of the intervention, both groups completed questionnaires 3 months after the program’s conclusion.

The second section of the questionnaire was designed to assess constructs associated with the Theory of Planned Behavior (TPB), including behavioral beliefs, normative beliefs, control beliefs, intention, and behavior. The researchers constructed the TPB questionnaire following Ajzen’s recommendations (1991) to establish the foundation for each construct operationalized within the research tool23,24. The questionnaire’s development was further informed by additional studies25.

Data were collected through a self-administered questionnaire in which participants provided their responses. The questionnaire’s content validity was established through evaluation by health education professionals and rheumatologists. A pilot study confirmed the questionnaire’s reliability using Cronbach’s alpha coefficient. The alpha values for the constructs under investigation ranged from 0.70 to 0.89, indicating acceptable internal consistency. Participants’ attitudes were evaluated using 12 Likert-scale items (ranging from 1 = “completely disagree” to 5 = “completely agree”). For subjective norms, the questionnaire included 11 items, such as “To prevent knee osteoarthritis, my friends believe I should maintain a proper weight” or “To prevent knee osteoarthritis, my family rarely uses stairs,” measured on a 5-point Likert scale ranging from 1 (“completely disagree”) to 5 (“completely agree”). Perceived behavioral control was assessed using 10 items, such as “Due to time constraints, it is impossible for me to exercise,” also rated on a 5-point Likert scale (1 = “completely disagree,” 5 = “completely agree”). Participants’ intention to engage in preventive behaviors was measured using 9 items, such as “I intend to exercise regularly to prevent osteoarthritis.” The behavior questionnaire comprised 9 items rated from 1 (“not at all”) to 5 (“always”). All construct scores were calculated as percentages. Data analysis was conducted using the Statistical Package for Social Sciences (SPSS) version 22. Descriptive statistics (mean and standard deviation), independent t-tests, chi-square tests, and paired t-tests were performed. The significance level was set at 0.05.

Results

The mean age was 51.22 years (SD ± 12.35) for women in the experimental group and 50.39 years (SD ± 12.64) for those in the control group. No significant difference in age was found between the groups (independent t-test, p > 0.05). Similarly, the mean body mass index (BMI) was 22.54 (SD ± 3.34) and 23.01 (SD ± 3.21) for the experimental and control groups, respectively, with no significant difference observed (independent t-test, p > 0.05). Chi-square analysis revealed no significant differences in education level (p = 0.34) or marital status (p = 0.28) between the groups. Table 1 presents the demographic characteristics of the participants.

Table 1 Distribution of women according to individual specifications.
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Independent t-tests revealed significant differences between the experimental and control groups in pre-intervention scores for attitude, subjective norms, perceived behavioral control, intention, and behavior. However, significant improvements in all constructs were observed only in the experimental group three months post-intervention, as evidenced by paired t-tests. The control group showed no significant changes over the same period (see Table 2).

Table 2 A comparison the mean score (as percentage) for attitude, subjective norms, perceived control behavior, intention and behavior in the experimental and control groups before and after the intervention.
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Discussion

Educational interventions serve as a crucial tool in promoting preventive behaviors. Their impact extends beyond individual well-being, demonstrably enhancing quality of life for individuals and reducing the economic burden placed on families and communities affected by chronic disorders. In particular, educating communities about adhering to safety principles and avoiding risky activities can effectively prevent knee osteoarthritis. Drawing upon the Theory of Planned Behavior (TPB) as a theoretical framework, this study aimed to promote preventive behaviors for knee osteoarthritis among women over 40 who reside in Fasa, Fars province, Iran. The current study demonstrated a significant increase in the experimental group’s mean score for attitudes toward preventive behaviors for knee osteoarthritis following the educational intervention. The implementation of group discussions and role-playing techniques effectively facilitated the participants’ adoption of preventive behaviors, enabling them to model proper techniques. To further reinforce these positive attitudes, participants received a training booklet upon completion of the program and weekly motivational messages. Mohammadi Zaidi et al. observed a significant positive shift in mean attitude scores among computer users in their experimental group compared to the control group (n = 150)26. Research by Morowatisharifabad et al. (2020) revealed a positive correlation between attitude and self-care behaviors of patients; specifically, attitude, subjective norms, and perceived behavioral control predicted 8% of the variance in knee OA self-care behavior intention, with attitude emerging as the strongest predictor27. However, Mazlumi et al.25 reported no significant change in participant attitudes following educational intervention. The findings of Jormand et al. (2022) corroborate the current study, demonstrating significant increases in mean attitude scores post-intervention28.

The intervention resulted in a significantly higher mean score for subjective norms within the experimental group compared to the control group. This improvement was potentially facilitated by two key strategies: first, the delivery of educational sessions by an orthopedist and a physiotherapist, who were perceived as credible sources of information and influential figures; and second, a dedicated session involving family members, who also act as influential figures, which targeted abstract subjective norms related to adopting preventive behaviors for knee osteoarthritis. Family support plays a crucial role in promoting preventive behaviors by creating supportive environments and offering consistent encouragement. Within the culture of Fars province and Fasa, women (mothers, wives, and daughters) play a central and prominent role in the family, and other family members prioritize women’s health over their own. When they perceive women to be at risk, they endeavor to provide additional care and reduce work-related and social pressures. Notably, studies utilizing the Theory of Planned Behavior (TPB) have demonstrated significant increases in mean subjective norm scores within the intervention group21,28.

According to Supriya and Latika (2023), the lifestyle and family structure prevalent in the Indo-Pak region, where living in joint families is the norm, may be beneficial to patients with rheumatoid diseases compared to other parts of the world where independent living is more common29. However, research by Mazlumi et al.25 and Mohammadi Zaidi et al.26 yielded contrasting results, indicating no significant impact on subjective norms.

The intervention employed training sessions to impart cognitive skills and new behaviors, while group discussions facilitated the exchange of constructive feedback and information. These combined strategies demonstrably enhanced perceived behavioral control within the experimental group. Of note, Robertson et al. observed that ergonomics training in workplaces significantly improved participants’ perceived control and posture30. Similarly, Mohammadi Zaidi et al. reported that the intervention group achieved higher perceived behavioral control scores at 3 and 6 months post-intervention compared to the control group26. Adding further support to these findings, Mazlumi et al. documented higher perceived behavioral control scores in their intervention group compared to the control group25. Martin’s study31 underscored the critical role of perceived behavioral control in facilitating the adoption of proactive behaviors. In the present study, the mean score for women’s intentions regarding preventive measures for knee osteoarthritis demonstrated a significant increase in the intervention group compared to the control group. In accordance with the Theory of Planned Behavior (TPB), the experimental group exhibited elevated mean scores for attitude, subjective norms, and perceived behavioral control three months after the educational intervention. This synergistic increase ultimately led to the promotion of intentional behavior, thus highlighting the positive impact of the intervention. Similarly, Mohammadi Zaidi et al.26 observed that educational intervention successfully promoted individuals’ intentions to improve their physical condition at both three and six months post-intervention.

Several studies, including those conducted by Akbarian Moghaddam et al.32, Vatanparast et al.33, Alami et al.34, and Rakhshani et al.35, have demonstrated the effectiveness of educational interventions based on the Theory of Planned Behavior (TPB) in increasing participants’ intention to engage in specific behaviors. Consistent with these findings, this study observed that a TPB-based educational intervention successfully promoted preventive behaviors for knee osteoarthritis among women over 40 in the experimental group. By focusing on the key factors influencing behavior change, the intervention employed strategies such as group discussions, active participation, and the clarification of benefits, barriers, and consequences. Additionally, it incorporated skill-building approaches to enhance communication, decision-making, problem-solving, and the acquisition of appropriate behaviors, while providing constructive feedback. Collectively, these elements contributed to the improved adoption of preventive behaviors against knee osteoarthritis within the experimental group. Furthermore, Kalte et al.‘s research lends support to the effectiveness of educational interventions, demonstrating their ability to reduce musculoskeletal risk factors through ergonomics training36.

Numerous studies have highlighted the positive impact of educational programs on health and performance outcomes. Viljanen et al.37 demonstrated a significant reduction in work-related ergonomic problems following an educational program. Similarly, Thomas et al.38 observed a decrease in knee pain among participants aged 45 and over who had undergone an educational intervention. Additionally, Albaladejo39, Coleman40, French41, Kroon42, and Tavafian43 all underscore the positive influence of educational interventions on participant performance. While Erfanian and Zorofi44 observed improvements in pain-related variables in both experimental and control groups after implementing resistance training modifications, Allegrante et al.45 reported performance gains among patients with knee osteoarthritis who participated in a walking training program. Duarte et al.46 examined the effectiveness of applying the Theory of Planned Behavior in predicting physical activity among Portuguese older adults with osteoarthritis. Of particular relevance, Mazlumi et al.25,47 found that a Theory of Planned Behavior (TPB)-based educational intervention led to a significant increase in participants’ behavioral scores within the experimental group, thereby demonstrating its potential to drive positive behavioral changes. The researchers acknowledge several limitations encountered during program implementation, including a lack of organizational and financial support, as well as the potential for social desirability bias inherent in self-reported questionnaires used to measure behavior and intention. Future studies should consider incorporating more objective measures, such as physical activity tracking or clinical assessments of knee function. It is recommended that future studies assess participants’ behavior through direct observation and trials, or require them to maintain daily records of their self-care behaviors.

Conclusion

The findings of the present study indicate that implementing educational interventions grounded in theoretical frameworks, particularly the Theory of Planned Behavior (TPB), aimed at preventing knee osteoarthritis holds promise for reducing its associated morbidity. To maximize effectiveness, such interventions should be specifically tailored through the incorporation of educational methodologies and alternative approaches that facilitate target group acceptance of the desired behavioral changes.