The thoracolumbar fascia is a large multi-layered dense connective tissue sheet covering the back from the sacrum and iliac crests to the thoracic cage. It has three layers: the posterior layer (covering and attached to the lumbar spinous processes and supraspinous ligaments), the middle layer (between erector spinae and quadratus lumborum), and the anterior layer (anterior to quadratus lumborum, continuous with the lateral arcuate ligament). The posterior layer is the thickest and most clinically important.
Encases the erector spinae and multifidus muscles posteriorly, providing a rigid sleeve that generates passive tension during trunk loading. Transmits force between the upper and lower limbs during gait. Provides attachment for the latissimus dorsi, gluteus maximus, and transversus abdominis.
The thoracolumbar fascia is central to low back pain biomechanics: disruption of the posterior layer by multiple posterior spine surgeries weakens the passive erector spinae sleeve. The transversus abdominis plane (TAP) block for abdominal wall anaesthesia deposits local anaesthetic in the fascial plane between the transversus and the internal oblique, bounded superiorly by the thoracolumbar fascia. Erector spinae plane (ESP) block deposits anaesthetic deep to the posterior thoracolumbar fascia layer for multilevel thoracic and lumbar analgesia.
Forced trunk flexion-rotation tears the posterior thoracolumbar fascia and the attached lumbar erector spinae attachments, producing acute posterior low back pain with spasm, loss of trunk extension, and a focal tender point; managed by progressive mobilisation, manual therapy, and core stabilisation addressing the fascial dysfunction.
