This cross-sectional observational study aims to investigate the relationship between Upper Cross Syndrome (UCS), a postural imbalance characterized by forward head posture and rounded shoulders, and Temporomandibular Disorder (TMD) in university students aged 18-35 years. TMD is a musculoskeletal condition affecting the jaw joint and masticatory muscles, commonly associated with pain, limited mandibular movement, and joint sounds. Since cervical posture and jaw function are anatomically and biomechanically interconnected, postural alterations seen in UCS may be associated with temporomandibular dysfunction. In this study, participants will undergo a single-session assessment including postural angle measurements (craniovertebral angle, head-shoulder angle, thoracic kyphosis angle), temporomandibular joint clinical examination, mandibular range of motion measurements, and completion of the OHIP-14 questionnaire. No intervention will be applied.The findings are expected to contribute to understanding the association between upper body posture and jaw dysfunction in young adults and may provide guidance for interdisciplinary assessment and preventive strategies.

Temporomandibular Disorder is a musculoskeletal condition affecting the temporomandibular joint and masticatory muscles, and it may lead to pain, mandibular movement limitations, joint sounds, and functional impairment. Upper Cross Syndrome is a postural imbalance involving the head, cervical spine, and shoulder girdle, commonly characterized by forward head posture, rounded shoulders, and increased thoracic kyphosis. The cervical spine, shoulder girdle, and temporomandibular region are anatomically and biomechanically interconnected. Alterations in head and shoulder posture may influence mandibular function through changes in muscle activity, joint loading, and cervical alignment. Therefore, postural changes associated with Upper Cross Syndrome may be related to temporomandibular symptoms and functional limitations. This observational cross-sectional study is designed to examine the correlation between Upper Cross Syndrome-related postural parameters and temporomandibular disorder-related clinical findings in university students aged 18-35 years. No intervention will be applied, and all assessments will be completed during a single assessment session. Participants will complete demographic and clinical information forms and the Oral Health Impact Profile-14 questionnaire to assess oral health-related quality of life. Temporomandibular joint assessment will include clinical examination and mandibular range of motion measurements, including maximum mouth opening, lateral deviation, and protrusion. Postural assessment will include craniovertebral angle, head-shoulder angle, and thoracic kyphosis angle measurements. Craniovertebral angle and head-shoulder angle will be assessed using standardized lateral-view photographs through the PhysioMaster® digital photogrammetry application. Thoracic kyphosis angle will be measured using the inclinometer function of the same application.The data obtained from this study will be used to examine the correlation between upper body postural alignment and temporomandibular dysfunction-related findings. The results may contribute to a better understanding of the relationship between posture and jaw function in young adults and may provide guidance for interdisciplinary assessment approaches

Inclusion Criteria:

• University students aged between 18 and 35 years
• Voluntary participation
• Signed informed consent

Exclusion Criteria:

• History of jaw surgery
• Presence of scoliosis or spinal disorders
• History of shoulder or spinal surgery
• Botulinum toxin injection in the facial or jaw region within the past year
• Diagnosis of rheumatologic disease
• Neurological, autoimmune, or significant psychological disorders
• Known cervical pathology within the past year

The study population consists of university students aged 18-35 years enrolled at the Faculty of Health Sciences, Gülhane. Participants are recruited voluntarily and represent a young adult population with similar academic workload and daily postural habits. The study includes students regardless of the presence or absence of temporomandibular dysfunction symptoms.

Individual participant data (IPD) will not be publicly shared due to privacy and confidentiality considerations. The dataset contains sensitive health-related information collected from university students, and no data-sharing agreement has been established.