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Although shear wave elastography (SWE) has been used to indirectly measure passive force in muscle tissues, it is unknown whether SWE can be utilized to evaluate passive force in capsule tissues. This study investigated the relationship between the shear elastic modulus and passive force in posterior shoulder capsules using SWE. Four middle and four inferior posterior shoulder capsules were dissected from four fresh-frozen cadavers. Passive force (0-400 g in 25-g increments) was applied to each capsule, and elasticity was measured simultaneously using SWE. The relationship between elasticity and passive capsule force was highly linear for all tested capsules (coefficients of determination range: 0.853-0.963). SWE is a valid and useful method of evaluating indirectly and noninvasively the passive force of the posterior shoulder capsules.