Objective: Percutaneous electrical nerve stimulation (PENS) appears to be effective for the treatment of musculoskeletal pain. The aim of this trial was to investigate the effects on disability and pain, as well as on the psychological aspects of adding PENS into an exercise program in patients with subacromial pain syndrome. Methods: A randomized, parallel-group clinical trial was conducted. Sixty patients with subacromial pain were allocated into exercise alone (n = 20), exercise plus PENS (n = 20), or exercise plus placebo PENS (n = 20) groups. Patients in all groups performed an exercise program twice daily for 3 weeks. Patients allocated to the PENS group also received four sessions of ultrasound-guided PENS targeting the axillar and suprascapular nerves. Patients allocated to the exercise plus placebo PENS received a sham PENS application. The primary outcome was related disability (Disabilities of the Arm, Shoulder, and Hand, DASH). Secondary outcomes included mean pain, anxiety levels, depressive symptoms, and sleep quality. They were assessed at baseline, one week after, and one and three months after. An analysis was performed using intention-to-treat with mixed-models ANCOVAs. Results: The results revealed no between-group differences for most outcomes (related disability: F = 0.292, p = 0.748, n2p = 0.011; anxiety: F = 0.780, p = 0.463, n2p = 0.027; depressive symptoms: F = 0.559, p = 0.575, n2p = 0.02; or sleep quality: F = 0.294, p = 0.747, n2p = 0.01); both groups experienced similar changes throughout the course of this study. Patients receiving exercise plus PENS exhibited greater improvement in shoulder pain at one month than those in the exercise (Δ −1.2, 95%CI −2.3 to −0.1) or the placebo (Δ −1.3, 95%CI −2.5 to −0.1) groups. Conclusions: The inclusion of four sessions of ultrasound-guided PENS targeting the axillar and suprascapular nerves into an exercise program did not result in better outcomes in our sample of patients with subacromial pain syndrome at one and three months after treatment.
