: Lumbar Spine
Comprehensive OMT reference hub, interactive cheat sheets, and board review notes for COMLEX Level 1, 2-CE, and 3.
Key Takeaway
Lumbar facets are oriented BM (Back, Medial), favoring flexion/extension. L5 sidebending engages the sacral oblique axis on the SAME side, while L5 rotation is OPPOSITE to sacral rotation. Psoas syndrome produces non-neutral L1/L2, ipsilateral L5 dysfunction, positive Thomas test, and contralateral piriformis tenderpoint.
1. Lumbar Anatomy & Biomechanical Rules
The lumbar spine consists of five robust vertebrae (L1–L5) designed to bear body weight. The facet orientation is BM (Back, Medial) in the sagittal plane, permitting substantial flexion and extension while severely restricting rotation.
| Parameter | Type I Lumbar Somatic Dysfunction | Type II Lumbar Somatic Dysfunction |
|---|---|---|
| Spinal Position | Neutral (no major flexion or extension). | Non-neutral (marked Flexion or Extension). |
| Segmental Involvement | Group of 3 or more adjacent vertebrae. | Single vertebral segment. |
| Coupling Rules | Sidebending and Rotation occur to OPPOSITE sides (e.g., $L1–L3\ N S_L R_R$). | Sidebending and Rotation occur to the SAME side (e.g., $L4\ F S_R R_R$). |
| Etiology | Postural stress, long-standing muscle imbalances, leg length discrepancy. | Acute trauma, sudden twisting, or heavy lifting. |
2. L5–Sacrum Interaction: The Rule of L5
Because L5 sits directly upon the sacral base, somatic dysfunctions at L5 dictate sacral mechanics according to three rigid principles tested on COMLEX.
THE 3 LAWS OF L5–SACRAL COUPLING: 1. Sidebending Law: L5 Sidebending engages the sacral oblique axis on the SAME SIDE (e.g., $L5\ S_L \rightarrow$ Left Oblique Axis). 2. Rotation Law: L5 Rotation is OPPOSITE to Sacral Rotation (e.g., $L5\ R_R \rightarrow$ Sacral Rotation Left $\rightarrow L-on-L$). 3. Torsion Type Law: - Type I L5 ($N S_L R_R$) $\rightarrow$ Forward Sacral Torsion ($R-on-R$ or $L-on-L$). - Type II L5 ($F/E S_L R_L$) $\rightarrow$ Backward Sacral Torsion ($R-on-L$ or $L-on-R$).
3. Differential Diagnosis of Low Back Pain
| Condition | Pathophysiology & Key Findings | Diagnostic Test / Imaging | OMT & Clinical Management |
|---|---|---|---|
| Psoas Syndrome | Hypertonicity/spasm of psoas muscle; causes non-neutral L1/L2, contralateral pelvic shift, ipsilateral L5 dysfunction. | Positive Thomas Test; tenderpoint 2 inches medial to ASIS; contralateral piriformis TP. | Counterstrain to psoas (patient supine, marked hip flexion & external rotation); MFR; avoid extension! |
| Herniated Nucleus Pulposus (HNP) | Posterolateral disc herniation compressing nerve root. L4–L5 affects L5 root; L5–S1 affects S1 root. | Positive Straight Leg Raise (SLR) & Lasegue test. MRI confirms location. | Conservative OMT (indirect techniques, MFR); avoid lumbar flexion & rotation; surgical consult if cauda equina. |
| Spinal Stenosis | Narrowing of spinal canal or neural foramina from osteophytes/facet hypertrophy. | Neurogenic claudication (leg pain with walking, relieved by sitting/flexion 'grocery cart sign'). | Flexion-based physical therapy; indirect OMT; epidural steroid injections. |
| Spondylolysis | Defect/fracture of the pars interarticularis without anterior slippage. | Oblique lumbar X-ray shows 'Scotty dog with collar'. | Activity modification; core stabilization; avoid hyperextension. |
| Spondylolisthesis | Anterior displacement of one vertebral body relative to the one below (usually L5 on S1). | Lateral X-ray shows step-off. Graded I (<25%) to IV (>75%). Palpable step-off defect. | Flexion exercises; abdominal strengthening; HVLA is ABSOLUTELY CONTRAINDICATED! |
4. Neurological Root Localization (L4, L5, S1)
| Nerve Root | Primary Motor Test | Reflex | Sensory Distribution |
|---|---|---|---|
| L4 Root (L3–L4 Disc) | Foot Inversion & Ankle Dorsiflexion (Tibialis Anterior) | Patellar Reflex | Medial malleolus & medial foot |
| L5 Root (L4–L5 Disc) | Great Toe Extension (Extensor Hallucis Longus) & Heel Walking | None (or Medial Hamstring) | Dorsum of foot & web space between 1st/2nd toes |
| S1 Root (L5–S1 Disc) | Foot Eversion & Plantarflexion (Gastrocnemius/Peroneus) & Toe Walking | Achilles Reflex | Lateral malleolus & lateral border of foot |
5. COMLEX Practice Knowledge Check
Source
Based on the publicly available table of contents and topic organization of OMM Review: A Comprehensive Review of Osteopathic Medicine. All notes are original; no copyrighted text, figures, or full source material is included.