Knee osteoarthritis (OA) is the most common chronic joint disorder, especially in older adults, and is a leading cause of pain, disability, and reduced quality of life. Patients with OA often experience pain and functional limitations that may contribute to psychological factors such as anxiety, depression, and kinesiophobia (fear of movement). Kinesiophobia is defined as an excessive and irrational fear of movement due to the belief that it will cause pain or re-injury, and it may further limit mobility and daily functioning.

The aim of this prospective, cross-sectional study is to investigate the prevalence of kinesiophobia among patients with primary knee osteoarthritis and to evaluate its relationship with pain severity and functional capacity. A total of 84 participants aged 40-85 years, diagnosed with knee OA, will be recruited from the Department of Physical Medicine and Rehabilitation, Ankara Training and Research Hospital. Data collection will include demographic and clinical information, quadriceps muscle strength, range of motion, and radiographic staging using the Kellgren-Lawrence scale. Outcome measures include the Tampa Scale for Kinesiophobia (TSK), Visual Analogue Scale (VAS) for pain, and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) for function.

This study will provide insights into the impact of kinesiophobia on pain and functional outcomes in knee OA and may help guide clinical strategies that address both physical and psychosocial factors in the management of this common condition.

Knee osteoarthritis (OA) is the most prevalent chronic joint disorder, characterized by progressive cartilage degeneration, abnormal remodeling of the subchondral bone, osteophyte formation, and joint pain that frequently results in disability. The knee joint is particularly vulnerable due to its weight-bearing function and high mechanical stress, making knee OA a leading cause of mobility impairment in older adults. While radiographic evaluation using the Kellgren-Lawrence (K/L) grading system remains the standard method for diagnosing and staging OA, radiographic severity does not always correlate with clinical symptoms such as pain and functional disability. This inconsistency suggests that psychosocial factors may play an important role in shaping the clinical presentation of knee OA.

Kinesiophobia, defined as an excessive and irrational fear of movement due to the anticipation of pain or re-injury, has been reported in various musculoskeletal disorders and post-surgical recovery. High levels of kinesiophobia are associated with worse pain perception, reduced functional capacity, and lower quality of life. In knee OA, the role of kinesiophobia remains controversial, with previous studies reporting inconsistent findings regarding its relationship with pain, functional limitation, and disease progression. Understanding this relationship is crucial, as addressing kinesiophobia may help to optimize rehabilitation outcomes and reduce disability in affected patients.

The present study is a prospective, cross-sectional observational study designed to assess the prevalence of kinesiophobia in patients with primary knee osteoarthritis and to examine its association with pain severity and functional status. A total of 84 patients, aged 40-85 years, with radiographically confirmed knee OA will be recruited from the Department of Physical Medicine and Rehabilitation, Ankara Training and Research Hospital. Patients with prior knee surgery, rheumatological disease, neuromuscular conditions, or systemic inflammatory disorders will be excluded.

Data collection will include demographic variables (age, sex, body mass index, occupation, comorbidities), physical examination findings (range of motion, quadriceps strength), and radiographic staging using the Kellgren-Lawrence scale. Patient-reported outcomes will be assessed using the Visual Analogue Scale (VAS) for pain, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) for function, and the Tampa Scale for Kinesiophobia (TSK), which has been validated in Turkish populations. Higher scores on these measures indicate greater pain, worse functional limitation, and higher levels of kinesiophobia.

All data will be analyzed using SPSS software. Normality will be assessed using the Kolmogorov-Smirnov test. Depending on data distribution, group comparisons will be made with Student's t test or Mann-Whitney U test, and relationships between kinesiophobia, pain, and function will be explored using correlation and regression analyses. A power analysis determined that a minimum of 84 patients will be required to achieve adequate statistical power at 80%.

By systematically evaluating kinesiophobia alongside clinical and radiographic features of knee OA, this study aims to clarify its role as a psychosocial factor influencing pain and disability. The findings are expected to contribute to improved patient assessment and may support the integration of psychological screening and targeted interventions in the management of knee osteoarthritis.

Inclusion Criteria:

• Age between 40-85 years
• Diagnosis of unilateral or bilateral primary knee osteoarthritis
• Duration of knee pain ≥ 3 months
• Radiographic confirmation of tibiofemoral OA (Kellgren-Lawrence grading)

Exclusion Criteria:

• Prior knee surgery
• Deep vein thrombosis
• Neuromuscular disease or neurological disorder
• Mental illness preventing participation
• Active infection or osteomyelitis
• Chronic periarticular infection
• Rheumatologic disease
• Immunodeficiency or systemic inflammatory disease
• Pregnancy

Adults aged 40-85 years with radiographically confirmed primary knee osteoarthritis, recruited from the Physical Medicine and Rehabilitation Clinic of Ankara Training and Research Hospital.

Individual participant data (IPD) will not be shared because the study is observational, involves a single-center hospital population, and collects sensitive clinical and psychosocial information that cannot be adequately de-identified for open sharing. Aggregate results will be reported in publications.