Lower limb
Lumbar plexus
Plexus lumbalis (L1-L4)
- Origin
- From the ventral rami of L1 to L4 (with a contribution from T12), within the psoas major
- Insertion
- Gives off the iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral and obturator nerves
- Function
- Supplies the abdominal wall below the umbilicus, the front and inner side of the thigh and the hip and knee extensors
- Innervation
- Ventral rami L1-L4
- Movement & chain
- Stretched by hip extension with knee flexion (reverse Lasegue test)
- Palpation
- Examination per nerve: quadriceps strength and knee reflex (L3-L4), sensation on the anterior thigh, adductor strength (obturator nerve)
- Clinical
- Plexus injury from a psoas haematoma during anticoagulation, compression after pelvic surgery, meralgia paraesthetica of the lateral femoral cutaneous nerve, diabetic amyotrophy
- Segmental innervation
- L1-L4
- In clinical practice
- Quadriceps weakness with an absent knee reflex in an anticoagulated patient: think of a psoas haematoma
- Region in the model
- Lower limb