# Measuring Cranivertebral Angle Reference Values in Adults Using Kinovea Software
###### Abstract
This software does not need the use of markers to make measurements, however, its reliability does improve when markers are used [26]. Examples of Kinovea's use in assessing motion include estimating body segment movements during falls [27], the height and velocity of vertical jumps [28], neck movement in the sagittal plane [29], knee angles during a variety of movements [30], and hip and knee kinematics in patients with low back pain [31]. [PERSON] et al. (2019) conducted a review and meta-analysis to investigate the relationship between neck pain and forward head posture [4]. When all age groups were analyzed together, there were no statistically significant differences in forward head posture between symptomatic and asymptomatic groups across the seven studies. However, when studies including adolescent or elderly participants were removed, a statistically significant mean difference of 4.84\({}^{\circ}\) (95% CI 0.14, 9.54) was identified between groups, suggesting that age may be a confounding factor in the relationship between forward head posture and neck pain. The same review reported a statistically significant correlation between forward head posture and neck pain intensity, and between forward head posture and disability as measured by the Neck Disability Index (NDI) [4]. A meta-analysis by [PERSON] and [PERSON] (2019) reported no difference in posture between adolescents with neck pain and asymptomatic adolescents [15]. However, their analysis included three low-quality studies with high heterogeneity of study data, which limits the reliability of their results [15]. Literature studying the relationship between head position and headaches is highly variable. A low level of evidence exists suggesting that individuals with tension headaches have a more forward head posture than those without tension headaches [6]. In the case of migraine headaches, moderate evidence suggests there is no difference in head position compared with asymptomatic subjects [6; 16]. With regard to primary headaches, the forward head position was greater in individuals with chronic headaches than in those with episodic headaches [7]. In the case of head position and cervicalogenic headaches, authors of one previous review were unable to perform a meta-analysis due to the low methodological quality of the available studies [16]. Meta-analyses show great heterogeneity in the results of studies investigating relationships between craniovertebral angle and neck pain or headaches. Despite this, relationships of varying strength have been reported between increased forward head posture (decreased craniovertebral angle) and neck pain, tension headaches, and primary chronic headaches. The lack of relationship reported between forward head posture and neck pain in the adolescent population suggests that age may be a confounding variable with respect to the craniovertebral angle. One existing meta-analysis presents valuable accumulated samples of craniovertebral angle values; however, the report does not include accumulated averages from all studies in the analysis [4]. Furthermore, no studies investigating the effect of age and sex on craniovertebral angle were identified. Therefore, it would benefit clinicians and researchers to establish the craniovertebral angle reference values in a healthy population and to investigate the effect of age and sex on head position in individuals without cervical pathology. The purpose of the present study is to identify craniovertebral angle reference values in healthy adults and describe the effect of age and sex on head position in the same population as measured by the craniovertebral angle. The authors hypothesize that there is a relationship between age, sex, and head position measured by craniovertebral angle in healthy adults.