 Subacromial impingement syndrome SAIS is a frequent cause of shoulder pain. Clinical trials investigating the effectiveness of manual therapy have demonstrated improvements in outcomes when manual therapy has been added to a program of therapeutic exercise. However, the these clinical trials 3 have significant limitations and generalizability. Two of the three 3 trials had a small number of subjects 14 22 subjects and all 3 trials had only short term follow up 12 weeks and used non-validated self report outcome measures. These limitations reduce the confidence with which clinicians can apply these results to the patients they treat with SAIS. Clear evidence is needed to justify the cost and clinician time required to perform manual therapy in the delivery of patient care. Therefore, the purpose of this randomized clinical trial is to examine the short-term and long-term effectiveness of manual therapy in addition to therapeutic exercise as compared to therapeutic exercise only in patients diagnosed with SAIS. 