Piriformis syndrome is a clinical condition characterized by buttock pain and/or sciatic-like symptoms, and its diagnosis remains challenging because there is no universally accepted diagnostic standard. This study aims to evaluate the diagnostic accuracy of commonly used diagnostic criteria and clinical tests for piriformis syndrome. Participants with suspected piriformis syndrome will undergo standardized physical examination and assessment of predefined diagnostic criteria. Ultrasound-guided injection of 5 mL of 2% lidocaine into the piriformis muscle will be used as the reference diagnostic procedure. A reduction of 50% or more in pain after injection will be considered confirmation of piriformis syndrome. The diagnostic performance of clinical tests and diagnostic criteria will be analyzed accordingly.

Piriformis syndrome is one of the possible causes of buttock pain and sciatica-like symptoms; however, its diagnosis is often difficult because of symptom overlap with lumbar radiculopathy, sacroiliac joint disorders, and other musculoskeletal conditions. In clinical practice, several physical examination maneuvers and diagnostic criteria are used, but their diagnostic accuracy has not been sufficiently established.

The aim of this study is to evaluate the diagnostic accuracy of predefined diagnostic criteria and commonly used clinical tests for piriformis syndrome. Adult participants with suspected piriformis syndrome will be recruited prospectively. All participants will undergo a standardized clinical assessment including history taking, physical examination, and evaluation of predefined diagnostic criteria and provocation tests. Clinical examinations will be performed by two physicians according to the study protocol.

As the reference diagnostic procedure, participants will undergo ultrasound-guided injection of 5 mL of 2% lidocaine into the piriformis muscle. The injection will be performed by an experienced physician under ultrasound guidance. Pain severity will be assessed before and after the procedure. A decrease of 50% or more in pain following injection will be accepted as confirmation of piriformis syndrome.

The diagnostic performance of each clinical test and diagnostic criterion set will be evaluated against this reference standard. Sensitivity, specificity, predictive values, likelihood ratios, and overall diagnostic accuracy will be analyzed. The findings of this study are expected to contribute to the development of a more standardized, reliable, and clinically applicable diagnostic approach for piriformis syndrome.

Inclusion Criteria:

• Adults aged 18 to 75 years
• Presentation with gluteal pain
• Pain on palpation in the piriformis region

Exclusion Criteria:

• History of injection to the lumbar, hip, or gluteal region within the last 3 months,including steroid, hyaluronic acid, or similar injections
• History of hip surgery
• Presence of active inflammatory rheumatic disease, including rheumatoid arthritis, ankylosing spondylitis, polymyalgia rheumatica, vasculitis, or similar conditions
• Active skin or subcutaneous soft tissue infection in the gluteal region
• Use of anticoagulant therapy that may contraindicate injection
• Presence of a bleeding disorder
• Uncontrolled diabetes mellitus and/or hypertension
• History of neurological disease
• Pregnancy or lactation
• Presence of a psychiatric disorder
• Known allergy to the injection agents
• History of malignancy

The plan for sharing individual participant data has not yet been determined.