Osteoarthritis (OA) is a degenerative joint disease characterized by structural changes such as cartilage loss and osteophyte formation, leading to functional limitations and disability. Pain in knee OA involves a complex pathophysiological structure including both nociceptive and neuropathic mechanisms. Identifying the neuropathic pain component is clinically significant for improving quality of life and functional recovery. This cross-sectional controlled clinical study aims to determine the prevalence of neuropathic pain in patients with knee OA and evaluate its impact on pain severity and functional status. Patients will be categorized based on the Douleur Neuropathique 4 (DN4) questionnaire and assessed using various pain and functional scales.

Osteoarthritis (OA) is a degenerative joint disease characterized by structural alterations, including focal cartilage loss, osteophyte formation, subchondral sclerosis, and synovitis. Given the growing elderly population, the prevalence of OA is rising, frequently leading to significant functional limitations and disability. Pain, the most prominent symptom of OA, serves as a critical measure for monitoring disease activity and treatment efficacy.

Recent evidence suggests that OA-related pain involves a complex pathophysiological structure, incorporating both nociceptive and neuropathic mechanisms. Studies indicate that approximately 19-37% of patients with knee OA exhibit symptoms consistent with neuropathic pain. Identifying this neuropathic component is clinically essential, as it may respond differently to conventional analgesics; thus, recognizing it is vital for optimizing functional recovery and quality of life.

This cross-sectional controlled clinical trial aims to determine the prevalence of neuropathic pain in patients with knee OA and evaluate its impact on pain severity and functional status. Participants diagnosed with knee OA according to the American College of Rheumatology (ACR) criteria will be recruited and categorized into two groups based on a Douleur Neuropathique 4 (DN4) questionnaire score threshold of 4/10.

For all participants, comprehensive demographic and clinical data, including age, body mass index (BMI), educational level, occupation, and marital status, will be recorded. To ensure consistency and minimize measurement error, all anthropometric assessments will be performed by a single researcher. The following standardized assessment tools will be administered to all participants: Visual Analog Scale (VAS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Knee Injury and Osteoarthritis Outcome Score-Physical Function Short Form (KOOS-PS).

Inclusion Criteria:

• Diagnosed with Knee OA according to ACR criteria.
• Knee pain for more than 3 months.
• Voluntary participation.

Exclusion Criteria:

• History of surgical intervention in the affected knee.
• History of trauma to the affected knee within the last 6 months.
• History of intra-articular injections (e.g., corticosteroids, hyaluronic acid, PRP) or physical therapy involving the affected knee within the last 6 months.
• Presence of severe psychiatric disorders such as severe depression, anxiety disorder, or psychosis.
• Diagnosis of central nervous system diseases, including Parkinson's disease or multiple sclerosis.
• Diagnosis of inflammatory arthritis, such as Rheumatoid Arthritis or Ankylosing Spondylitis.
• Severe cognitive impairment.
• Chronic decompensated cardiac, renal, or hepatic failure.
• Severe psychiatric, neurological, or kognitive disorders.

Decompensated cardiac, renal, or hepatic failure.

The source population for this cross-sectional controlled study is the adult patient population diagnosed with knee osteoarthritis (OA) according to the American College of Rheumatology (ACR) criteria, recruited from the Physical Medicine and Rehabilitation outpatient clinic at Istanbul Physical Therapy and Rehabilitation Training and Research Hospital.

De-identified individual participant data (IPD), including all demographic, clinical, and primary/secondary outcome measures will be shared with qualified researchers. The sharing period will commence 6 months after article publication and conclude 1 year thereafter. Data access requests must be accompanied by a methodologically sound proposal and will be granted upon the corresponding author's approval and the execution of a Data Use Agreement (DUA) to strictly ensure confidentiality and adherence to ethical guidelines.

Beginning 6 months and ending 1 year following article publication

Qualified researchers who present a methodologically robust proposal aimed at fulfilling the objectives of the approved project