Understanding body stiffness, jaw problems and fear of movement

Axial rigidity and loss of spinal mobility commonly observed in Parkinson's disease (PD) lead to postural deformities and substantial reductions in trunk flexibility. This condition can impair the biomechanics of the craniocervical and lumbopelvic kinetic chain, potentially exerting a negative impact on temporomandibular joint (TMJ) functions. In this context, the planned study aims to determine whether differences exist in spinal mobility, axial rigidity, and kinesiophobia levels between individuals with PD with and without Temporomandibular Disorders (TMD), and to investigate whether a biomechanical relationship exists between TMD and spinal mobility, axial rigidity, and kinesiophobia levels in this population. The study will be conducted face-to-face at the Neurology Outpatient Clinic of Hatay Mustafa Kemal University Research and Training Hospital. Individuals aged 40-75 years, diagnosed with PD, staged between 1.5 and 4 according to the Hoehn and Yahr Scale, with a Mini-Mental State Examination score of 24 or higher (MMSE ≥ 24), and in the "ON" state during the evaluation will be included. Individuals with a history of cervical, lumbar, maxillofacial, or TMJ surgery that could directly affect spinal mobility and posture; acute orthopedic or rheumatologic disorders that would preclude testing (e.g., advanced Ankylosing Spondylitis); comorbid neurological conditions (e.g., stroke, multiple sclerosis); complete edentulism or severe disruption of oral anatomy; active toothache; pregnancy or suspected pregnancy; and severe psychiatric disorders will be excluded. Written informed consent will be obtained from all participants, and the study will be conducted on a voluntary basis. All data will remain confidential and be utilized solely for scientific purposes. In this cross-sectional study, evaluations will be carried out in a single session for each participant. Following the recording of demographic and clinical characteristics, the presence of TMD will be assessed using the Fonseca Anamnestic Index, jaw range of motion with a millimeter ruler, and spinal mobility using the modified-modified Schober test, tragus-to-wall distance, intermalleolar distance, and occiput-to-wall distance measurements. Axial rigidity will be evaluated using item 3.3 (Rigidity) of the Movement Disorder Society-Sponsored Revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS), posture will be assessed using MDS-UPDRS item 3.13 (Posture) alongside craniovertebral angle measurement, and kinesiophobia will be assessed via the Tampa Scale for Kinesiophobia. The resulting findings are expected to contribute to understanding the impact of spinal mobility, axial rigidity, and kinesiophobia on the temporomandibular system in PD, offering valuable clinical guidance for assessment, physiotherapy, and multidisciplinary neurological rehabilitation pathways.