Association between neck muscle size and physical features in individuals with chronic non-specific neck pain: A systematic review.

Despite multiple studies investigating neck muscle structure in people with chronic non-specific neck pain (CNP), findings on the relationship between neck muscle size and commonly assessed physical features are inconsistent, highlighting the need for systematic synthesis and evaluation of the available evidence. This systematic review examines the association between neck muscle size and commonly assessed physical features including neck strength, endurance, range of motion, proprioception and head posture in individuals with CNP. A systematic search was conducted across MEDLINE, EMBASE, PubMed, CINAHL Plus, and Web of Science from inception to 21 October 2024. The included studies focused on adults with CNP, examining the correlation between measures of neck muscle morphology and physical features. Exclusion criteria included traumatic neck pain, neck surgery, and radiculopathy. Risk of bias was assessed using a modified Newcastle-Ottawa Scale and the certainty of evidence was evaluated using the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) approach. A narrative synthesis was used to summarise the findings. Of the 5,912 identified records, eight studies were included, comprising 246 participants. The narrative synthesis of the included studies identified significant correlations between the cross-sectional area (CSA) of longus colli and longus capitis with neck endurance, longus capitis CSA with neck proprioception, and longus colli CSA with measures of postural sway. Based on very low certainty of evidence, reduced neck muscle size is associated with lower neck endurance, altered proprioception, and increased postural sway in individuals with CNP. CRD42024570776 (PROSPERO).