Masseter Muscle Thickness in Individuals With Chronic Neck Pain

Inclusion Criteria: * Be between the ages of 18 and 45 * Have neck pain that has persisted for at least 3 months * Agree to participate in the study voluntarily and provide written informed consent Exclusion Criteria: * History of cervical spine surgery or severe trauma * Diagnosis of cervical radiculopathy, myelopathy, or neurological disease * Rheumatic, inflammatory, or systemic musculoskeletal diseases * Diagnosed temporomandibular joint disorder (TMD) * Diagnosis of bruxism or a pronounced habit of teeth clenching/grinding * History of manual therapy, injection, or surgical intervention in the face, jaw, or neck region within the last 6 months * Currently undergoing orthodontic treatment or history of orthodontic treatment within the last 6 months * Cognitive impairment or conditions that prevent understanding and responding to questionnaires