Gluteus Maximus: Origin, Insertion, Nerve, Action & Clinical Testing

The Gluteus Maximus is the largest and heaviest muscle in the human body. It forms the bulk of the buttock region. It is the primary extensor of the hip and plays a critical role in maintaining upright posture, climbing stairs, and running.

[Image of Gluteus Maximus muscle anatomy]

Quick Anatomy Snapshot

Origin (Proximal)	Posterior gluteal line of the Ilium, dorsal surface of the Sacrum and Coccyx, and the Sacrotuberous Ligament.
Insertion (Distal)	Superficial fibers (75%): Insert into the Iliotibial (IT) Tract. Deep fibers (25%): Insert into the Gluteal Tuberosity of the Femur.
Nerve Supply	Inferior Gluteal Nerve (L5, S1, S2).
Blood Supply	Superior and Inferior Gluteal Arteries.
Primary Actions	Hip Extension: Primary power extensor (e.g., standing up, climbing). External Rotation: Turns the thigh outward. Stabilization: Stabilizes the knee in extension via the IT tract.

Deep Dive: The Powerhouse

The Gluteus Maximus is unique to humans in its size, developed to support our bipedal (two-legged) locomotion.

1. The IT Band Connection

Surprisingly, the majority of the muscle does not attach directly to the femur bone. About 75% of the fibers insert into the Iliotibial (IT) Tract. This means when the Glute Max contracts, it tightens the IT band, which helps stabilize the lateral knee.

2. Postural Control

When you are standing still, the Gluteus Maximus is actually relaxed. However, as soon as you lean forward slightly, it kicks in to prevent you from falling on your face. It acts as a major anti-gravity muscle to keep the trunk upright.

Physio Corner: Clinical Relevance

💪 Functional Fact: The Gluteus Maximus is the "Sit-to-Stand" muscle. It is relatively quiet during casual walking on flat ground but fires intensely during running, jumping, or climbing stairs.

Palpation

Have the patient lie prone (face down). Ask them to squeeze their buttocks together or lift their thigh off the table with the knee bent. The large, fleshy mass of the buttock is the Gluteus Maximus. You can palpate the origin at the sacrum and trace it laterally to the greater trochanter/IT band.

⚠️ Clinical Pathology: Gluteus Maximus Lurch
If the Gluteus Maximus is paralyzed (Inferior Gluteal Nerve injury), the patient cannot forcefully extend the hip. To compensate during walking, they will thrust their trunk backward (posterior lurch) at heel strike to maintain balance and lock the hip into extension passively.

Manual Muscle Testing (MMT)

To test the Gluteus Maximus, we must isolate it from the Hamstrings (which also extend the hip).

Testing Tip: Keep the knee flexed to at least 90 degrees. This puts the Hamstrings in "active insufficiency" (too short to work well), forcing the Gluteus Maximus to do the lifting.

Step-by-Step Procedure (Oxford Scale)

Grade	Patient Action & Resistance
Grade 3, 4, 5 (Against Gravity)	Position: Prone (face down). Knee flexed to 90°. Action: Patient lifts the thigh off the table (extends hip), keeping the knee bent. Resistance: Applied at the distal posterior thigh (just above the knee), pushing down towards the table. Grade 3: Clears the table. Grade 4/5: Holds against strong pressure.
Grade 2 (Gravity Eliminated)	Position: Side-lying on the test side (difficult) or Side-lying on non-test side with leg supported. Action: Patient extends the hip (moves thigh backward) with knee flexed. Result: Full range of motion.
Grade 0, 1 (Palpation)	Action: Palpate the upper and lower gluteal fibers. Cue: "Squeeze your butt cheeks together." Grade 1: Muscle contraction felt. Grade 0: No activity.

Frequently Asked Questions

Do we sit on the Gluteus Maximus?

No. When you sit, the lower border of the Gluteus Maximus slides up and outward. You are actually sitting on the Ischial Tuberosity (sit bone), cushioned by the ischial bursa and fat pad, not the muscle itself.

Does it abduct or adduct?

Both! The Upper Fibers assist in Abduction (moving leg away). The Lower Fibers assist in Adduction (moving leg in). However, the entire muscle acts as an external rotator.

What is Lower Crossed Syndrome?

This is a postural imbalance characterized by tight hip flexors (Iliopsoas) and weak glutes (Gluteus Maximus). This leads to an anterior pelvic tilt and "sway back" (hyperlordosis).

Test Your Knowledge: Gluteus Maximus Quiz

1. Which nerve supplies the Gluteus Maximus?

2. The majority of Gluteus Maximus fibers insert into the:

3. What is the primary action of Gluteus Maximus?

4. During MMT, why is the knee flexed?

5. Where does the Gluteus Maximus originate?

6. Paralysis of the Gluteus Maximus causes which gait abnormality?

7. Besides extension, the Gluteus Maximus is a strong:

8. Which ligament provides an origin for the Gluteus Maximus?

9. The Gluteus Maximus acts on the knee joint via the:

10. Lower Crossed Syndrome involves weakness of the Glutes and tightness of the:

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.
• Kendall, F. P. (2005). Muscles: Testing and Function, with Posture and Pain. 5th ed. Lippincott Williams & Wilkins.