This single-center observational study aims to investigate neuropathic pain descriptors and their relationship with central sensitization in patients diagnosed with subacromial pain syndrome (SAPS) who have had shoulder pain for at least 3 months. A total of 82 participants aged 19 years or older will be recruited from the Physical Medicine and Rehabilitation outpatient clinic of Izmir City Hospital. After obtaining informed consent, participants will complete validated questionnaires assessing pain severity (VAS), neuropathic pain characteristics (painDETECT), central sensitization (Central Sensitization Inventory), and shoulder function (SPADI). Range of motion will be measured using a goniometer. No imaging or invasive procedures will be performed. Using the central sensitization scale and pain detect, the presence or absence of the 7 pain descriptors will be investigated in patients with subacromial pain syndrome with or without central sensitization and neuropathic pain pattern and it will be investigated whether the contribution of hyperalgesia, one of these pain descriptors, to neuropathic pain and central sensitization in patients with subacromial pain syndrome is greater than the contribution of other pain descriptors.The results of this study are expected to provide insight into pain mechanisms and guide clinical management in patients with SAPS.

Inclusion Criteria:

1. Clinical diagnosis of subacromial pain syndrome (SAPS)
2. Age ≥ 19 years
3. Shoulder pain lasting for at least 3 months
4. Shoulder pain intensity rated as 3 or higher on the Visual Analog Scale (VAS) in the past week
5. Positive findings on the following clinical tests:

Hawkins-Kennedy test Painful arc test Infraspinatus muscle strength test

Exclusion Criteria:

1. History of inflammatory disease involving the shoulder joint
2. History of neurological disorders
3. History of prior shoulder surgery
4. Positive drop arm test
5. Loss of passive range of motion in the shoulder joint
6. Presence of muscle strength loss
7. Structurally confirmed shoulder pathology based on imaging studies
8. Full-thickness tear of the rotator cuff muscles
9. Presence of neurodeficit in the upper extremity
10. Diagnosis of cancer or active infection
11. Use of medications for neuropathic pain within the past 3 months for any reason

This study will be conducted with 82 patients aged 19 years and older who have been admitted to the PTR outpatient clinic of Izmir City Hospital with shoulder pain and diagnosed with subacromial pain syndrome and who have had shoulder pain for at least 3 months.