Adductor Magnus: Origin, Insertion, Nerve, Action & The "Hybrid" Muscle

The Adductor Magnus is the largest, deepest, and most complex muscle of the adductor group. It is often referred to as a "hybrid" muscle because it has two distinct parts that function differently: an adductor part (similar to the other groin muscles) and a hamstring part (acting like a hip extensor).

[Image of Adductor Magnus muscle anatomy]

Quick Anatomy Snapshot

Anatomical Part	Adductor Part (Pubofemoral)	Hamstring Part (Ischiocondylar)
Origin	Inferior Ramus of Pubis and Ramus of Ischium.	Ischial Tuberosity (Sit bone).
Insertion	Gluteal tuberosity, Linea Aspera, Medial Supracondylar Line.	Adductor Tubercle of the Femur.
Nerve Supply	Obturator Nerve (Posterior Division) - L2, L3, L4.	Tibial Nerve (part of Sciatic Nerve) - L4.
Primary Actions	Adduction, Flexion (superior fibers).	Adduction, Extension of the hip.

Deep Dive: The Anatomical Archway

The Adductor Magnus makes up the bulk of the medial thigh flesh. Its two parts are separated by a key anatomical feature.

1. The Adductor Hiatus

Near the distal femur, there is a gap between the insertion of the adductor part (on the Linea Aspera) and the hamstring part (on the Adductor Tubercle). This gap is called the Adductor Hiatus.

It serves as a passageway for the Femoral Artery and Vein to pass from the anterior thigh (Adductor Canal) to the posterior knee (Popliteal Fossa), where they change names to the Popliteal Artery and Vein.

2. "The Fourth Hamstring"

The posterior portion of the Adductor Magnus arises from the Ischial Tuberosity (just like the Semitendinosus, Semimembranosus, and Biceps Femoris). It is innervated by the Tibial nerve and extends the hip. Anatomically and functionally, it essentially is a hamstring muscle that simply fails to cross the knee joint.

Physio Corner: Clinical Relevance

💪 Functional Fact: The Adductor Magnus is a massive stabilizer of the pelvis during the stance phase of walking. Recent EMG studies suggest it is arguably a more powerful Hip Extensor than the Hamstrings or Gluteus Maximus in certain ranges of motion (especially when the hip is flexed, like climbing stairs).

Palpation

Because it is deep to the Gracilis and Adductor Longus, the bulk is hard to isolate. However, the tendon of the hamstring portion is easily palpable. Locate the medial epicondyle of the femur (inner knee). Move slightly superiorly to feel a small bony bump—the Adductor Tubercle. The cord-like tendon inserting here is the Adductor Magnus.

⚠️ Clinical Pathology: Deep Groin Pain
Strains to the Adductor Magnus often present as "deep" groin pain or pain near the sit bone (Ischial Tuberosity), making it easy to confuse with a high hamstring strain. Resisted adduction with the hip in neutral or extension will specifically target this muscle.

Manual Muscle Testing (MMT)

Testing requires differentiating the two functional parts.

Testing Tip: To bias the Adductor Magnus over the Longus/Brevis, ask the patient to adduct while you also resist extension.

Step-by-Step Procedure (Oxford Scale)

Grade	Patient Action & Resistance
Grade 3, 4, 5 (Against Gravity)	Position: Side-lying on the affected side (test leg on bottom). Top leg held up by therapist. Action: Patient lifts the bottom leg up towards the ceiling. Resistance: Applied at the distal medial thigh, pushing down. Grade 3: Clears the table. Grade 4/5: Holds against strong pressure.
Grade 2 (Gravity Eliminated)	Position: Supine. Leg abducted. Action: Patient slides the leg to the midline. Result: Full range of motion.
Grade 0, 1 (Palpation)	Action: Palpate the tendon at the Adductor Tubercle (medial knee). Cue: "Squeeze your knees together." Grade 1: Tendon tension felt. Grade 0: No activity.

Frequently Asked Questions

Why does it have a dual nerve supply?

Because of its dual embryonic origin. The anterior part develops with the adductor group (Obturator nerve), while the posterior part develops with the hamstring group (Tibial nerve).

Does Adductor Magnus cross the knee?

No. Even though the hamstring portion originates on the Ischial Tuberosity, it inserts on the Adductor Tubercle of the femur. Therefore, it has no action on the knee joint (unlike the true hamstrings).

What structures pass through the Adductor Hiatus?

The Femoral Artery and Femoral Vein pass through to become the Popliteal vessels. The Saphenous Nerve does not pass through; it exits the adductor canal superficially.

Test Your Knowledge: Adductor Magnus Quiz

1. Which nerve supplies the "Hamstring Portion" of the Adductor Magnus?

2. Where does the Hamstring Portion originate?

3. What is the Adductor Hiatus?

4. Where does the hamstring portion insert?

5. Which movement is unique to the hamstring portion of Adductor Magnus (compared to other adductors)?

6. The Adductor Magnus is the ________ muscle in the medial compartment.

7. After passing through the Adductor Hiatus, the Femoral Artery becomes the:

8. Which part of the Obturator nerve supplies the Adductor Magnus?

9. True or False: Adductor Magnus helps stabilize the pelvis during walking.

10. The Adductor Magnus acts as a synergist to which muscle during hip extension?

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.
• Neumann, D. A. (2016). Kinesiology of the Musculoskeletal System. 3rd ed. Elsevier.