Can a fluid injection between muscle layers ease piriformis pain?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Age 18 to 70 years. * Buttock or gluteal pain that may radiate to the posterior thigh and/or leg. * Medical history and physical examination findings consistent with piriformis syndrome. * Tenderness on palpation over the piriformis muscle. * A positive result on at least one of the following piriformis provocation maneuvers: FAIR, Freiberg, Pace, or Beatty. * Exclusion of lumbar radiculopathy, clinically significant hip pathology, and other major causes of buttock or leg pain by clinical assessment and, when clinically indicated, review of available routine imaging. * Ability to understand and sign the written informed consent form. * Ability and willingness to attend the scheduled follow-up visits. Additional criterion for randomization: \- At least a 50 percent early reduction in overall pain after the single ultrasound-guided local anesthetic piriformis injection. Exclusion Criteria: * Active lumbar radiculopathy, clinically significant lumbar disc herniation, spinal stenosis, or another spinal disorder that could explain the participant's symptoms. * Clinically significant neurological deficit. * Marked limitation of lumbar spine and/or hip range of motion. * Previous surgery involving the lumbar spine or hip region. * Pregnancy or breastfeeding. * Known allergy or hypersensitivity to lidocaine or another local anesthetic used in the study. * Current anticoagulant treatment or a clinically significant coagulation disorder. * Active infection at the injection site. * Body mass index greater than 35 kg/m². * Active inflammatory or infectious disease that may affect participant safety or study assessments. * Active psychiatric condition that may interfere with informed consent, adherence to study procedures, or outcome assessment. * Uncontrolled hypertension. * Uncontrolled diabetes mellitus. * Decompensated cardiac, hepatic, or renal failure. * Vascular or neoplastic disease that could explain the symptoms or increase the risk of the study procedures. * Injection, dry needling, or a similar intervention in the gluteal region within the previous 3 months. * Inability or unwillingness to complete the scheduled follow-up visits.