Discussion
knee osteoarthritis, joint stiffness, anxiety, pain
OSTEOARTHRITIS, BLIND, KNEE OSTEOARTHRITIS
This study aimed to compare the effects of knee strengthening exercises (Group 1) and exercises based on polyvagal theory combined with knee strengthening exercises (Group 2) in females with grade II knee OA. The study assessed various outcome variables, including WOMAC scores (joint pain, joint stiffness, functional limitations, and the overall index) and WHOQOL scores measuring QoL; general health; and the physical, psychological, social, and environmental domains. Additionally, autonomic function was measured by heart rate variability (HRV) measures, which were analyzed in the time and frequency domains.Polyvagal theory, proposed by Porges, suggests that the vagus nerve plays a crucial role in regulating the autonomic nervous system and influencing emotional states, stress responses, and social engagement. Engaging in activities that stimulate the vagus nerve, such as the exercises described, may promote relaxation, reduce anxiety, and enhance emotional regulation. These outcomes could ultimately contribute to a reduction in perceived pain and an increase in quality of life in patients with knee osteoarthritisThe WOMAC assessment for knee OA is a sensitive tool, well suited for detecting changes in symptoms and function over time or in response to interventions. This evaluation captures the patient's perspective, facilitating a comprehensive assessment of the impact of knee OA on daily life and functioningMuscle and skeletal problems constitute over a quarter of nonlethal health losses, with pain being the most significant contributorAnother study by Morone and Greco reinforces the findings that guided imagery and relaxation offer clinical pain management benefits for individuals with knee OAIn individuals with osteoarthritis, pain is the most prevalent complaint and a primary contributor to reduced health-related quality of life (HRQoL). In this study, both groups demonstrated significant improvements across various domains of quality of life, including overall quality; general health; and physical, psychological, social, and environmental aspects. Notably, Group 2 exhibited more substantial enhancements in overall quality of life, general health, psychological, social, and environmental domains than Group A, which underwent vagal nerve stimulation-based exercise. The improvement in the physical domain is attributed to the 6-week exercise regimen, a sentiment that aligns with Smith et al.’s findings, emphasizing the efficacy of a scalable exercise program in enhancing the well-being and function of hip and knee OA patientsVagal stimulation, in line with the polyvagal theory, is also emphasized by Wang et al., who suggest that practices such as yoga—a form of physical and relaxation exercise—have a systemic effect. By stimulating parasympathetic pathways, yoga reduces perceived pain and improves QoLThe observed changes in HRV parameters can be attributed to the stimulation of the vagal nerve. This emphasizes the contention of the polyvagal theory that the physiological state is not merely a correlate but a fundamental component of emotions and moods. Within this theoretical framework, the autonomic state functions as an intermediary variable that influences our perception and evaluation of environmental stimuli. The reflexive assessment of cues as neutral, positive or threatening can vary based on an individual's physiological state. Functionally, changes in an individual’s state can lead to a shift in the accessibility of different brain structures, facilitating social communication or eliciting defensive responses such as fight/flight or shutdownThe study had a few limitations that should be noted. It had a small sample size, exclusively female participants, and a lack of long-term follow-up. While generalization to the wider population should be approached with caution, the study's findings still contribute to a broader understanding of the potential benefits of the interventions within this specific subset of patients. The decision to include female participants only was driven by the fact that knee osteoarthritis is more commonly observed in females than in males. Evaluating the sustainability and durability of the benefits conferred by polyvagal exercises in the long term could provide a more comprehensive understanding of their effects and guide clinical recommendations. Furthermore, there was no control group, and blinding procedures were not implemented. The inability to implement blinding in this study is attributable to the nature of the interventions employed, which made it a practical challenge to blind participants and researchers to the group assignments, as the participants themselves needed to be aware of the specific exercises they were performing. The study relied on self-reported measures and did not use objective measures. A total reliance on self-reported measures, without the use of objective assessments, introduces the potential for measurement bias due to participants' subjective perceptions and recall biases. Integrating objective measures such as biomechanical assessments or biomarkers would offer a more comprehensive understanding of the interventions' effects. Finally, the dropout rate was 10%, which may have affected the representativeness of the final sample and introduced potential bias.