Myofascial pain can be diagnosed by the presence of one or more myofascial trigger points (MTrPs), defined as hyperirritable spots in taut bands of skeletal muscle fibers palpable by hand. The treatment of myofascial pain primarily relies on the inactivation of MTrPs, often through manual pressure techniques or dry needling. In manual pressure techniques, the physiotherapist applies increasing pressure directly to the MTrP. In dry needling, acupuncture-like filiform needles are applied to the same point. There are two types of dry needling: superficial dry needling, which penetrates only the skin and superficial muscle, and deep dry needling, which involves inserting a needle directly into the MTrP. The sole or adjunct effectiveness of dry needling treatment targeting the trapezius and infraspinatus muscles has been investigated, particularly in patients with shoulder myofascial pain syndrome. In the study we are planning, a double-blinded efficacy trial will be conducted in patients with shoulder myofascial pain syndrome, where real and sham dry needling applications will be performed under ultrasound guidance, with both the patient and the evaluator blinded. This study design has the potential to make a significant contribution to the literature in this field.

It is planned to enroll 50 patients aged between 18 and 80 years who have been diagnosed with Shoulder Myofascial Pain Syndrome into the study. After signing informed consent forms, eligible patients will be randomized into two different groups using a random number table (randomizer.org) according to inclusion and exclusion criteria. In the study, neither the patient nor the evaluator will know which group they are in; only the physician administering the dry needling treatment will be aware. At the beginning of the study, during weekly follow-ups, and at the end of the study, non-interventional assessment tests will be conducted. Minimal intervention, drug-free dry needling treatment will be administered to patients twice in total, once a week, each session lasting approximately 10-20 minutes with ultrasonographic guidance. Throughout the study period, all patients in both groups will be instructed in detail on the daily exercises they need to perform (trapezius stretching and infraspinatus stretching exercises), as well as on important considerations (avoiding prolonged static positions, etc.). They will be encouraged to perform these exercises daily and mark their completion. Additionally, they will be informed about the selection and usage of medications (only paracetamol) that they can use when necessary, along with instructions on adherence and marking on the provided follow-up form. The entire process will be monitored weekly through the follow-up form provided to the patients.

Inclusion Criteria:

• Clinically diagnosed with Shoulder Myofascial Pain Syndrome associated with Infraspinatus trigger point.
• Having a shoulder pain Visual Analog Scale (VAS) score of 6 or higher.
• Ability to read and write

Exclusion Criteria:

• History of shoulder surgery and frozen shoulder syndrome.
• Lesions, atrophy, or scars in the skin around the shoulder.
• Having undergone physiotherapy targeting the shoulder in the last 6 months.
• Undergoing an interventional procedure for shoulder pain in the last 3 months.
• Having used steroids in the last 1 month.
• Special conditions such as epilepsy, pregnancy, injection phobia, etc.
• Inability to comply with the restriction on the use of steroid and non-steroidal anti-inflammatory drugs during the treatment period.

In the dry needling application, patients will be blinded to the groups they are randomized into. The evaluator will also be unaware of which group the patients belong to. The practitioner will perform the procedures in both groups using ultrasound guidance, targeting the standard trigger points in the painful shoulder's trapezius and infraspinatus muscles in the study group, and targeting subcutaneous fatty tissue in the same regions in the sham group.