Association of Intrascapular Myofascial Trigger Points and Thoracic Hypokyphosis with the Risk of Development of Shoulder Impingement Syndrome: A Cross-Sectional Study

Background: Shoulder impingement syndrome is a frequent musculoskeletal disorder linked to scapular dysfunction and thoracic postural deviations. Intrascapular myofascial trigger points disrupt biomechanics, while thoracic hypokyphosis impairs scapulothoracic rhythm. Objective: To determine the association of intrascapular myofascial trigger points and thoracic hypokyphosis with the risk of developing shoulder impingement syndrome. Methodology: A cross-sectional study was conducted among 176 participants at a physiotherapy clinic in Peshawar from September 2024 to February 2025. Adults aged 20-50 years with shoulder pain lasting at least three months were included. Intrascapular myofascial trigger points were assessed by palpation and pressure pain threshold testing. The thoracic kyphosis angle was measured using a flexible curve ruler and categorized as hypokyphosis (<20°). Shoulder impingement syndrome was confirmed through Neer, Hawkins-Kennedy, and painful arc tests. Data were analyzed using chi-square and logistic regression. Results were expressed as odds ratios with 95% confidence intervals, and statistical significance was set at a p-value less than 0.05. Results: Out of 176 participants, 62 (35.2%) demonstrated thoracic hypokyphosis, and 104 (59.1%) had active intrascapular myofascial trigger points. The prevalence of shoulder impingement syndrome was 46.6% (n=82). Logistic regression revealed that thoracic hypokyphosis (OR=2.14, 95% CI=1.21-3.78, p=0.00) and trigger points (OR=2.87, 95% CI=1.64-5.01, p<0.00) were independently associated with shoulder impingement syndrome. The combined presence of both risk factors showed the highest association (OR=4.12, 95% CI=2.02-8.38, p<0.00). Conclusion: Intrascapular myofascial trigger points and thoracic hypokyphosis are significantly associated with shoulder impingement syndrome risk. Early screening and management of postural and myofascial dysfunctions may help prevent or reduce impingement syndrome in at-risk populations.