159 patients diagnosed with subacromial impingement were included in this randomized control trial to determine the effectiveness of different injectable substances for the treatment of subacromial impingement. Subjects were randomized to one of three groups receiving hyaluronic acid (HA) with lidocaine, corticosteroid with lidocaine, or lidocaine alone (control). All three treatments produced a reduction in pain for 60% of patients allocated to each group. The use of corticosteroids appeared to provide the greatest reduction in pain over the short term (3, 6, 12 weeks). The use of HA did not appear to provide any benefits when compared to the control group.