# Measuring Cranivertebral Angle Reference Values in Adults Using Kinovea Software
###### Abstract  
The clinical examination of patients with cervical spine pathology includes measures of posture, mobility, strength, and stability. The forward head position as measured by craniovertebral angle (CVA) has been suggested as a risk factor for cervical spine pathology. The purpose of this study was to describe CVA reference values in healthy adults and assess the relationship with age and sex. This prospective cross-sectional observational study measured the CVA in 122 healthy adults using digital analysis of a lateral view photograph. To facilitate this analysis, a marker was placed at the level of the C7 verteb, with the tragus of the ear visible in the photograph. The CVA was measured using Kinovea 0.8.15 software, where the CVA was calculated using the intersection of a horizontal line with a line joining the spinous process of C7 and the tragus of the ear. Mean CVA values were 48.76\({}^{\circ}\) (6.77) across all participants, 50.07\({}^{\circ}\) (6.63) for females, and 47.46\({}^{\circ}\) (6.71) for males. Linear regression analysis indicated significant relationships with age and with sex. The study established CVA reference values in healthy adults and identified a significant difference in head position between males and females and a 1.6\({}^{\circ}\) decrease in CVA per decade of increased age. craniovertebral angle; head; neck; posture; cervical vertebrae; reference values; photogrammetry 2024 2024 14 8 It has been suggested that increased thoracic kyphosis could facilitate a forward head posture [18; 19]. Forward head posture can affect the muscular balance of the neck, head, shoulder girdle, and upper thoracic muscles due to a combination of shortened and overactivated muscles, and weak and lengthened muscles. The muscles prone to be shortened and overactivated are the subocipitals, sternocleidomastoid, levator scapula, upper trapezius, scalenes, and pectoralis major and minor bilaterally [20]. In addition, muscles that tend to be weak and lengthened are the deep neck flexors, lower trapezius, and rhomboids bilaterally [20]. Finally, an increase in masticatory muscle electromyographic activity on the same side of the upper trapezius muscle myofasical trigger points has been identified [11]. The combination of forward head posture with thoracic kyphosis and the protraction of the shoulder girdles has been termed \"upper crossed syndrome\" by [PERSON] [21]. This syndrome not only impacts neck and shoulder function but also may decrease the forced vital capacity and one-second expiratory volume due to spinal and rib cage motion restriction and posture alterations [22; 23]. Other functions like proprioception could be altered by changes in the head position leading to fatigue in other muscles, coordination deficits, and dizziness [24]. The method most frequently used to measure head posture is the craniovertebral angle (CVA), defined as the angle of the line passing through the tragus of the ear and the spinous process of the seventh cervical vertebra with respect to the horizontal. This angle represents the position of the head in relation to the position of C7 vertebra, with a smaller angle representing a greater forward head position, and a higher craniovertebral angle representing a more erected position with the head closer to the plumb line as the craniovertebral angle is increased. Traditionally, the forward head posture has been measured using a plumb line and a tape measure or with a goniometer. With the emergence of commercially available high-speed motion capture cameras, powerful computer systems, and image processing software, more precise measurements of forward head postures are now possible. For example, Kinovea, a free-to-use and open-source software, has been shown to provide good reliability compared with three-dimensional optical motion capture systems [25; 26]. Kinovea is a two-dimension motion analysis software widely used to analyze movement and measure angles in digital images like photographs and videos [25].