Quadratus Lumborum: Origin, Insertion, Nerve, Action & "The Hip Hiker"

The Quadratus Lumborum (QL) is the deepest muscle of the posterior abdominal wall. Often mistaken for a back muscle, it essentially connects the pelvis to the spine and the rib cage. It is a common source of lower back pain and is famous for its role in "hiking" the hip during walking.

[Image of Quadratus Lumborum muscle anatomy]

Quick Anatomy Snapshot

Origin (Inferior)	Posterior part of the Iliac Crest and the Iliolumbar Ligament.
Insertion (Superior)	Inferior border of the 12th Rib and Transverse Processes of L1-L4 vertebrae.
Nerve Supply	Anterior (Ventral) Rami of T12, L1, L2, L3, L4.
Blood Supply	Lumbar Arteries and Iliolumbar Artery.
Primary Actions	Unilateral: Lateral flexion of trunk; Elevation of Hemipelvis ("Hip Hiking"). Bilateral: Extension of lumbar spine; Fixes 12th rib during forced expiration.

Deep Dive: The Rectangular Stabilizer

The name "Quadratus" implies a square or rectangular shape. The muscle is enclosed by the anterior and middle layers of the Thoracolumbar Fascia.

1. The Fiber Layers

Though it looks like one sheet, the QL has three distinct fiber directions:
• Iliocostal fibers: Ilium to 12th Rib (Vertical).
• Iliolumbar fibers: Ilium to Lumbar Vertebrae (Diagonal).
• Lumbocostal fibers: Lumbar Vertebrae to 12th Rib (Diagonal).

2. Relation to Organs

The QL lies directly posterior to the Kidneys (separated by fascia and fat), the Colon (ascending/descending), and the Psoas Major muscle. Pain in the QL can sometimes be mistaken for kidney pain, and vice-versa.

Physio Corner: Clinical Relevance

💪 Functional Fact: "Hip Hiking" is the QL's signature move. If you are in a cast or have a fused knee, you use your QL to lift your hip up so your foot can clear the ground during the swing phase of walking.

Palpation

Have the patient lie on their side (test side up) or prone. Place your hand in the space between the bottom of the rib cage (12th rib) and the top of the hip (iliac crest), lateral to the Erector Spinae muscles. Ask the patient to "shrug their hip toward their shoulder." You will feel the QL contract deep in the flank.

⚠️ Clinical Pathology: "The Joker of Low Back Pain"
Dr. Travell nicknamed the QL the "Joker" because its referred pain patterns are misleading. Trigger points in the QL often refer sharp pain to the SI Joint, the buttock, and the greater trochanter, mimicking Sciatica or Hip Bursitis.

Manual Muscle Testing (MMT)

We test the ability to elevate the pelvis (Hip Hiking).

Testing Tip: Ensure the patient does not laterally flex their trunk using their abdominals. The motion should come from the pelvis pulling up.

Step-by-Step Procedure (Oxford Scale)

Grade	Patient Action & Resistance
Grade 3, 4, 5 (Against Resistance)	Position: Supine or Prone. Legs extended. Action: Patient hikes the pelvis on one side (brings iliac crest toward ribs). "Shorten your leg." Resistance: Therapist grasps the ankle and pulls the leg downward (traction), trying to lengthen the leg. Grade 3: Can hike hip. Grade 4/5: Holds against strong traction.
Grade 0, 1 (Palpation)	Action: Palpate deep in the lumbar flank, lateral to the erector spinae. Cue: "Try to pull your hip up." Grade 1: Deep tension felt. Grade 0: No activity.

Frequently Asked Questions

Is QL an abdominal or back muscle?

Technically, it is a muscle of the Posterior Abdominal Wall. However, functionally and clinically, it is treated as a deep back muscle because it extends and stabilizes the lumbar spine.

Does it help with breathing?

Yes. It stabilizes the 12th rib during forced expiration. By holding the rib down, it provides a stable anchor for the diaphragm to contract against during inspiration.

Why does QL get tight from sitting?

When sitting (especially with poor posture or leaning to one side), the QL is often contracted isometrically to stabilize the spine or hold a lateral lean. This chronic low-level contraction leads to trigger points and shortness.

Test Your Knowledge: Quadratus Lumborum Quiz

1. Which nerve supplies the Quadratus Lumborum?

2. What is the unique unilateral action of the QL?

3. Where does the QL insert superiorly?

4. Which organ lies directly anterior to the QL?

5. The QL acts on the 12th rib to assist in:

6. Where does the QL originate?

7. To MMT the QL, you apply resistance to the:

8. The QL is located deep to which muscle group?

9. Why is the QL called "The Joker" of back pain?

10. True or False: The QL attaches to the Lumbar Transverse Processes.

References

• Moore, K. L., Dalley, A. F., & Agur, A. M. R. (2018). Clinically Oriented Anatomy. 8th ed. Philadelphia: Wolters Kluwer.
• Standring, S. (2016). Gray's Anatomy: The Anatomical Basis of Clinical Practice. 41st ed. Elsevier.
• Travell, J. G., & Simons, D. G. (1999). Myofascial Pain and Dysfunction: The Trigger Point Manual. 2nd ed. Williams & Wilkins.