A 42-year-old female presents with 4 months of left-sided buttock pain that occasionally radiates to the posterior thigh but never below the knee. Pain is rated 6/10, worse with prolonged sitting on hard surfaces, getting out of a car, and rolling over in bed. She is a runner and noticed symptom onset after increasing her weekly mileage. She has a history of two vaginal deliveries. Physical therapy focusing on lumbar stabilization has not helped.

No lumbar tenderness. Negative lumbar extension-rotation. Positive Fortin finger test: patient points directly to the left posterior superior iliac spine (PSIS) as the epicenter of pain. SI joint provocation tests: positive distraction, compression, thigh thrust, and FABER tests on the left (4/6 positive). Gaenslen test positive on the left. No radicular findings: full strength, intact sensation, symmetric reflexes.

MRI lumbar spine is unremarkable with no significant disc or facet pathology. X-ray pelvis shows mild sclerotic changes at the left SI joint. No sacral fracture or sacroiliitis.