Stretching Positions for the Posterior Capsule of the Glenohumeral Joint

Background: Various stretches have been introduced for the posterior shoulder; however, little quantitative analysis to measure stretching of the posterior capsule has been performed. Hypothesis: The current shoulder stretching program is not sufficient to stretch the entire posterior capsule. Study Design: Controlled laboratory study. Methods: Using 8 fresh-frozen cadaver shoulders (average age, 82.4 years), 8 stretching positions for the posterior capsule were simulated by passive internal rotation. Stretching positions of 0°, 30°, 60°, and 90° of elevation in the scapular plane; 60° of flexion; 60° of abduction; 30° of extension; and 60° of flexion and horizontal adduction were adopted. Strain was measured in the upper, middle, and lower parts of the capsule. The measurement of strain was instituted from reference length. Results: With internal rotation, mean strain on the upper capsule was 3.02% at 0° of elevation and 3.35% at 30° of extension. Strain on the middle capsule at 0° and 30° elevation was 0.78% and 4.77%, respectively; on the lower capsule, it was 5.65% and 2.24% at 30° and 60° of elevation, respectively, and 2.88% at 30° of extension. Increase in strains of the upper, middle, and lower capsule with internal rotation at 0°, 30°, and 60° of elevation were statistically significant, respectively ( P < .01). Other shoulder positions demonstrated no positive strain values. Conclusions: Based on the results of this cadaver study, large strains on the posterior capsule of the shoulder were obtained at a stretching position of 30° of elevation in the scapular plane with internal rotation for the middle and lower capsule, while a stretching position of 30° of extension with internal rotation was effective for the upper and lower capsule. Clinical Relevance: The current posterior capsule stretching program of the shoulder was not sufficient to stretch the entire posterior capsule. Keywords: shoulder posterior capsule strain stretching cadaver