The aim of this study is to evaluate the accuracy of blinded invasive interventions (dry needling) on the deep paraspinal muscles of the lumbar region (iliocostalis lumborum, longissimus thoracis, and multifidus) to reach the anatomical target. The accuracy of the interventions will be evaluated observationally with ultrasonography after the procedure.

*Method:*

• All interventions will be performed by a physical medicine and rehabilitation specialist with clinical experience.
• After each intervention, the needle tip position will be evaluated by a second specialist with *high-resolution linear probe ultrasound*.
• Targeted muscles:
• *Iliocostalis lumborum (ICL)*
• *Longissimus thoracis (LT)*
• *Multifidus (M)*
• Interventions will be performed from the right side, between the L2-L5 levels.
• A total of *three different dry needling applications* will be performed for these three muscles for each participant.
• When a total of *20 participants* is planned, *60 injection attempts* will be analyzed.
• Will be used only for post-hoc observational validation purposes.
• No pharmacological agent will be administered during the intervention, only dry needling will be performed.

Inclusion Criteria:

• Adults aged 18-65

  • Individuals with nonspecific low back or back pain and planned physical therapy
  • Individuals with suspected MPS, especially in the paraspinal muscles
  • Individuals with indications for dry needling
  • Those who can cooperate with the procedure and give written consent

Exclusion Criteria:

• * Anticoagulant use

  • History of spine surgery, deformity, severe scoliosis
  • Regional skin lesion or infection
  • Patients who cannot cooperate
  • Pregnancy
  • Serious systemic diseases such as malignancy or neurological disease