Subacromial impingement syndrome is one of the most common causes of shoulder pain and may negatively affect daily activities and quality of life. While shoulder pain is usually considered nociceptive, some patients may also have a neuropathic pain component, which can influence symptom severity and treatment outcomes. In addition, psychological factors such as pain catastrophizing and adherence-related behavior may play an important role in recovery.

This prospective observational study aims to evaluate the presence of neuropathic pain in patients with subacromial impingement syndrome and to investigate its relationship with pain catastrophizing and adherence-related behavior. Patients undergoing a standard physical therapy program will be assessed at the beginning and after completion of treatment using validated clinical scales.

The findings of this study may help to better understand the interaction between pain characteristics, psychological factors, and adherence-related behavior, and contribute to the development of more individualized rehabilitation strategies

Subacromial impingement syndrome (SIS) is one of the most common causes of shoulder pain and represents a substantial proportion of rotator cuff-related shoulder disorders. Although it is traditionally associated with nociceptive and mechanical pain mechanisms, recent evidence suggests that a subset of patients may also present with a neuropathic pain component and central sensitization, which may contribute to increased pain intensity, functional impairment, and poorer treatment outcomes.

In addition to biological factors, psychosocial variables play a critical role in chronic musculoskeletal pain. Pain catastrophizing, reflecting exaggerated negative cognitive and emotional responses to pain, has been associated with increased disability and delayed recovery. Similarly, adherence-related behavior may influence clinical outcomes, particularly in the context of physical therapy and exercise-based interventions. Understanding the interaction between neuropathic pain, catastrophizing, and adherence-related behavior may help identify clinically relevant subgroups and guide individualized rehabilitation strategies.

This study is designed as a prospective observational cohort study conducted in patients diagnosed with subacromial impingement syndrome who are referred to an outpatient physical therapy and rehabilitation clinic. Participants who meet the inclusion criteria will be consecutively enrolled and will receive a standard conservative physical therapy program. No additional or experimental interventions will be applied within the scope of the study.

Clinical and patient-reported outcome measures will be used to assess pain characteristics, psychological factors, functional status, and adherence-related behavior.

The primary aim of the study is to evaluate the relationship between neuropathic pain and pain catastrophizing in patients with subacromial impingement syndrome. Secondary analyses will explore the associations between these variables and adherence-related behavior, as well as clinical outcomes such as pain intensity and functional status.

The findings of this study are expected to contribute to a better understanding of the multidimensional nature of shoulder pain and to support the development of more targeted and individualized rehabilitation approaches.

Inclusion Criteria:

• Unilateral subacromial impingement syndrome lasting at least 3 months
• Planned to start a 10-session physical therapy program
• Willing and able to provide informed consent

Exclusion Criteria:

• Upper extremity entrapment neuropathy or polyneuropathy
• History of diabetes mellitus
• Inflammatory rheumatic disease, infection, or malignancy
• Frozen shoulder
• History of shoulder fracture, dislocation, or surgery
• Complete rotator cuff tear on magnetic resonance imaging
• Calcific tendinitis
• Shoulder steroid injection or physical therapy within the previous 3 months
• Use of medication for neuropathic pain
• Pregnancy
• Cognitive impairment preventing completion of questionnaires

The study population consists of adult patients aged 18-65 years diagnosed with unilateral subacromial impingement syndrome who are referred to an outpatient physical therapy and rehabilitation clinic. Patients with symptoms lasting at least three months. Participants scheduled to undergo a standard conservative physical therapy program will be included.

Individual participant data will not be shared due to institutional policies and ethical considerations regarding patient confidentiality.