Pectineus: Origin, Insertion, Nerve, Action & Groin Strain

The Pectineus is a flat, quadrangular muscle situated at the anterior part of the upper and medial aspect of the thigh. It acts as a bridge between the anterior compartment (hip flexors) and the medial compartment (adductors). Because of its dual function, it is a common site for groin injuries in athletes.

[Image of Adductor Longus muscle anatomy]

Quick Anatomy Snapshot

Origin (Proximal)	Pectineal Line (Pecten Pubis) on the superior ramus of the Pubis.
Insertion (Distal)	Pectineal Line of the Femur (running from the lesser trochanter to the linea aspera).
Nerve Supply	Femoral Nerve (L2, L3). (Sometimes receives a branch from the Accessory Obturator Nerve).
Blood Supply	Medial Circumflex Femoral Artery.
Primary Actions	Adduction: Pulls the thigh towards the midline. Flexion: Flexes the hip joint.

Deep Dive: The "Hybrid" Muscle

The Pectineus is anatomically interesting because it sits on the border between two major muscle groups.

1. The Femoral Triangle Floor

The Pectineus forms the Medial Floor of the Femoral Triangle (along with the Iliopsoas which forms the lateral floor). This puts it in direct contact with the femoral vessels.

2. The Nerve Exception

Most adductor muscles (Longus, Brevis, Magnus) are innervated by the Obturator Nerve. The Pectineus, however, is primarily innervated by the Femoral Nerve (like the Quadriceps). This classifies it anatomically as an anterior thigh muscle, even though functionally it is a strong adductor.

Physio Corner: Clinical Relevance

💪 Functional Fact: The Pectineus is a "power" muscle for movements like crossing your legs (flexion + adduction) or kicking a soccer ball with the inside of the foot (passing).

Palpation

Caution: The Pectineus lies deep to the Femoral Artery and Vein.
To palpate safely:
1. Locate the Femoral Pulse in the groin.
2. Move your fingers just medial to the pulse.
3. Ask the patient to gently adduct and flex the hip. The Pectineus will firm up just lateral to the Adductor Longus tendon.

⚠️ Clinical Pathology: Groin Strain
Pectineus strains are common in soccer players and sprinters. Pain is felt deep in the groin, distinct from the more superficial Adductor Longus tendon. Pain is reproduced by resisted hip flexion and adduction simultaneously.

Manual Muscle Testing (MMT)

To isolate the Pectineus, we combine its two primary actions.

Testing Tip: Think of the "Cross-Legged" position. The muscle pulls the thigh up and in.

Step-by-Step Procedure (Oxford Scale)

Grade	Patient Action & Resistance
Grade 3, 4, 5 (Against Gravity)	Position: Sitting (legs dangling). Action: Patient lifts the thigh (flexion) while simultaneously pulling it inward (adduction). Think "hacking" a footbag. Resistance: Applied at the distal medial thigh (above knee), pushing down and out (extension and abduction). Grade 3: Completes motion against gravity. Grade 4/5: Holds against resistance.
Grade 2 (Gravity Eliminated)	Position: Supine. Leg supported. Action: Patient slides heel up towards the opposite shin (flexion + adduction). Result: Full range of motion.
Grade 0, 1 (Palpation)	Action: Palpate just medial to the femoral pulse in the groin. Cue: "Try to bring your knee up and in." Grade 1: Deep contraction felt. Grade 0: No activity.

Frequently Asked Questions

Why is it called Pectineus?

It comes from the Latin word Pecten, meaning "comb." It originates from the Pectineal line (sharp ridge) on the pubis bone.

Is it a medial or anterior muscle?

It is a transitional muscle. Anatomically (by nerve supply), it is Anterior. Functionally (by action), it is Medial (Adductor). It is often grouped with the adductors in textbooks.

Does it rotate the hip?

This is debated. Most sources agree it assists in Medial (Internal) Rotation, though some older texts suggest lateral rotation. EMG studies support a role in stabilization during rotation.

Test Your Knowledge: Pectineus Quiz

1. Which nerve primarily supplies the Pectineus?

2. The Pectineus forms the floor of which anatomical structure?

3. Where does the Pectineus insert?

4. What are the primary actions of the Pectineus?

5. Which vessel lies immediately superficial to the Pectineus?

6. Where does the Pectineus originate?

7. In MMT, resistance is applied in which direction?

8. Which muscle lies directly lateral to the Pectineus?

9. Some individuals have an accessory nerve supply to Pectineus from:

10. True or False: Pectineus is the most anterior of the adductor muscles.

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.
• Magee, D. J. (2014). Orthopedic Physical Assessment. 6th ed. Elsevier.