Knee osteoarthritis is a common degenerative joint disease in which pain severity often does not fully correspond with radiographic disease severity. Psychological processes such as rumination and worry may contribute to differences in pain perception and functional limitation among patients with similar structural disease burden.

The purpose of this observational study is to investigate the relationships between radiographic osteoarthritis severity, pain severity, functional limitation, rumination, and worry in patients with knee osteoarthritis. Radiographic severity will be assessed using the Kellgren-Lawrence classification. Participants will complete the Penn State Worry Questionnaire, the Ruminative Thought Style Questionnaire, the Visual Analog Scale (VAS), and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC).

The study aims to determine whether rumination and worry are associated with pain severity and functional impairment independently of radiographic osteoarthritis severity. Findings from this study may improve understanding of the biopsychosocial mechanisms underlying pain perception in knee osteoarthritis and may support the development of multidisciplinary treatment approaches that incorporate psychological factors into patient assessment and management.

Knee osteoarthritis is one of the most common degenerative joint diseases and represents a major cause of pain, disability, and reduced quality of life in older adults. Although radiographic severity is commonly used to evaluate disease progression, clinical symptoms often show substantial variability among patients with similar structural findings. This discrepancy suggests that factors beyond structural joint degeneration may contribute to pain perception and functional impairment in osteoarthritis.

Rumination is a repetitive and difficult-to-control cognitive process characterized by persistent focus on negative thoughts, bodily symptoms, or distressing experiences. Similarly, worry reflects excessive and uncontrollable concern about potential threats or adverse outcomes. Both cognitive processes may increase attentional focus on pain-related sensations and contribute to heightened pain perception, emotional distress, and functional limitation. Previous studies have demonstrated associations between psychological factors and chronic pain outcomes; however, the simultaneous effects of rumination and worry on osteoarthritis-related pain and functional status, while considering radiographic disease severity, remain insufficiently investigated.

The purpose of this observational study is to evaluate the relationships between radiographic osteoarthritis severity, pain severity, functional limitation, rumination, and worry in patients with knee osteoarthritis. Participants presenting with knee pain and diagnosed with osteoarthritis based on radiographic evaluation will be included. Radiographic severity will be graded according to the Kellgren-Lawrence classification system. Psychological and clinical assessments will include the Penn State Worry Questionnaire, the Ruminative Thought Style Questionnaire, the Visual Analog Scale (VAS), and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC).

The primary objective of the study is to determine whether rumination and worry are independently associated with pain severity and functional limitation after accounting for radiographic osteoarthritis severity. Secondary analyses will investigate the relationships between psychological measures and WOMAC subscales, as well as the extent to which psychological factors may contribute to symptom severity disproportionate to structural disease burden.

The findings of this study may contribute to a better understanding of the biopsychosocial mechanisms underlying pain in knee osteoarthritis and may support the development of multidisciplinary treatment strategies that integrate psychological assessment into routine clinical care.

Inclusion Criteria:

• Age 18 years or older
• Diagnosis of knee osteoarthritis confirmed by radiographic evaluation
• Ability and willingness to provide informed consent
• Ability to complete study questionnaires

Exclusion Criteria:

• Presence of comorbid conditions that may cause knee pain other than osteoarthritis
• Analgesic medication use within the previous week
• Cognitive impairment or psychiatric conditions that may interfere with questionnaire completion, including dementia, intellectual disability, or psychotic disorders

Adults presenting with knee pain to the orthopedic and traumatology outpatient clinic who are diagnosed with knee osteoarthritis based on radiographic evaluation will be enrolled in this observational study. Participants will undergo assessment of radiographic osteoarthritis severity, pain severity, functional limitation, rumination, and worry using validated clinical and psychological questionnaires.

Individual participant data collected during the study will not be shared. Only de-identified aggregate study results may be presented in scientific publications or presentations.