This study aims to evaluate muscle thickness in patients with unilateral Greater Trochanteric Pain Syndrome using ultrasonography and to compare these findings with healthy individuals. The primary objective is to determine whether piriformis muscle thickness differs between patients and controls. Secondary objectives include assessing gluteus medius and gluteus maximus muscle thickness, side-to-side differences in piriformis and gluteal muscle thickness, and the presence of Deep Gluteal Syndrome.

This observational cross-sectional study investigates ultrasonographic muscle morphology and associated clinical findings in patients with unilateral Greater Trochanteric Pain Syndrome (GTPS), focusing on piriformis and gluteal muscle thickness, symptom severity, and Deep Gluteal Syndrome-related findings.

Participants with unilateral GTPS and healthy controls are recruited from outpatient clinical settings. The clinical diagnosis of Greater Trochanteric Pain Syndrome is based on the presence of lateral hip pain in combination with at least two of the following findings: tenderness over the greater trochanter on palpation, pain during a 30-second single-leg stance test, or supportive ultrasonographic findings.

Ultrasonographic evaluations are performed bilaterally to measure piriformis, gluteus medius, and gluteus maximus muscle thickness. For each muscle, three measurements are obtained, and the mean value is used for analysis. Inter-side differences between affected and unaffected hips in the GTPS group and between both hips in the control group are calculated to assess asymmetry.

In the control group, the mean values of both hips are calculated and used as reference values. Comparisons are performed between affected and unaffected hips within the patient group. In addition, muscle thickness of the affected and unaffected hips in the GTPS group is compared separately with the control group mean values for each muscle. Inter-side differences in muscle thickness are also compared between patients and healthy controls. Trochanteric bursal fluid and Doppler signal changes are also evaluated using ultrasonography.

The presence of Deep Gluteal Syndrome is determined based on clinical criteria, defined as at least one clinical finding together with at least two positive standardized clinical provocation tests. Patients are categorized as Deep Gluteal Syndrome-positive or negative accordingly.

Symptom severity is assessed using the VISA-G (Victorian Institute of Sport Assessment-Gluteal) questionnaire. Correlation analyses are performed to evaluate the association between VISA-G scores and inter-side differences in muscle thickness.

Inclusion Criteria:

• Adults aged 18 years or older
• Diagnosis of unilateral Greater Trochanteric Pain Syndrome

Exclusion Criteria:

• Presence of lumbar radiculopathy
• Presence of hip or spinal osteoarthritis
• History of lumbar spine or lower extremity surgery
• Presence of neurological disorders affecting muscles or peripheral nerves
• Pregnancy
• Presence of cognitive impairment or neuropsychiatric conditions limiting participation
• Unwillingness to participate
• Regular participation in physical exercise (defined as more than two sessions per week)

Adults with unilateral Greater Trochanteric Pain Syndrome and healthy individuals without hip pain or known musculoskeletal disorders are being recruited. Participants are evaluated using ultrasonography in an outpatient clinical setting.