Background Posterior capsule tightness (PCT) and shoulder impingement syndrome (SIS) symptoms are both associated with altered shoulder biomechanics and impairments. However, their combined effect on kinematics, pain, range of motion (ROM), strength, and function remain unknown. Objective The purpose of this study was to determine if the combination of PCT and SIS affects scapular and humeral kinematics, glenohumeral joint ROM, glenohumeral joint external rotation strength, pain, and function differently than does either factor (PCT or SIS) alone. Design The design was a cross-sectional group comparison. Methods Participants were placed into 1 of 4 groups based on the presence or absence of SIS and PCT: control group (n = 28), PCT group (n = 27), SIS group (n = 25), and SIS + PCT group (n = 25). Scapular kinematics and humeral translations were quantified with an electromagnetic motion capture system. Shoulder internal rotation and external rotation ROM, external rotation strength, and pain and Shoulder Pain and Disabilities Index scores were compared between groups with ANOVA. Results The SIS group had greater scapular internal rotation (mean difference = 5.13°; 95% confidence interval [CI] = 1.53°–8.9°) and less humeral anterior translation (1.71 mm; 95% CI = 0.53–2.9 mm) than the other groups. Groups without PCT had greater internal rotation ROM (16.05°; 95% CI = 5.09°–28.28°). The SIS + PCT group had lower pain thresholds at the levator scapulae muscle (108.02 kPa; 95% CI = 30.15–185.88 kPa) and the highest Shoulder Pain and Disabilities Index score (∼ 44.52; 95% CI = 33.41–55.63). Limitations These results may be limited to individuals with impingement symptoms and cannot be generalized to other shoulder conditions. Conclusions Decreased ROM and lower pain thresholds were found in individuals with both impingement symptoms and PCT. However, the combination of factors did not influence scapular and humeral kinematics.

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