The 'sham posterior shoulder tightness' group will receive home stretches and manual therapy of similar durations to the 'posterior shoulder tightness' group, but delivered to structures that have no known direct structural influence on the posterior shoulder. The intention is for subjects to receive a similar dose of manual therapy to control for the generic effects of manual therapy, which may have pain relieving mechanisms. The sham intervention will be controlled for time and attention in order to create a comparable attention-control group. Using this design it may be possible to determine if there is any additional benefit to treating posterior shoulder tightness in combination with high quality rehabilitation for patients with shoulder impingement syndrome.