Pectineus

Introduction

Introduction to Pectineus

The pectineus is a flat, quadrangular muscle situated in the superomedial aspect of the anterior thigh. It is a transitional muscle between the anterior and medial compartments of the thigh, often considered part of the medial (adductor) group. The pectineus flexes, adducts, and medially rotates the hip joint. It forms part of the floor of the femoral triangle and is a landmark for the femoral vessels and nerve. Its dual innervation from the femoral and obturator nerves is unique and clinically significant, reflecting its intermediate position between the two compartments. Pectineus is clinically relevant in groin strains, as a surgical landmark in hip approaches, and as a potential site of referred pain from hip joint pathology.

Study

1. Origin and Insertion

The pectineus originates from the pecten pubis (pectineal line of the pubic bone) on the superior surface of the superior pubic ramus, and from a small area on the anterior surface of the pubis between the iliopubic eminence and the pubic tubercle. Its fibres pass inferolaterally and posteriorly to insert onto the pectineal line of the femur, a roughened ridge extending from the lesser trochanter to the linea aspera. The insertion is posterior to the insertion of the iliopsoas on the lesser trochanter.

2. Relations

Anteriorly, the pectineus is covered by the fascia lata and forms the medial part of the floor of the femoral triangle. The femoral vessels and the femoral nerve lie directly anterior to the upper part of the muscle. The great saphenous vein crosses the muscle superficially. Medially, it is related to the adductor longus. Laterally, it is separated from the iliopsoas tendon by the femoral nerve. Posteriorly, it lies on the capsule of the hip joint and the obturator externus muscle. The medial circumflex femoral artery passes between the pectineus and the iliopsoas tendon.

3. Nerve Supply

The pectineus receives a dual innervation. The anterior part of the muscle is innervated by the femoral nerve (L2, L3, L4), typically by a branch from the nerve to the pectineus which arises from the femoral nerve just after it enters the femoral triangle. The posterior part of the muscle is innervated by the anterior branch of the obturator nerve (L2, L3, L4). This dual innervation reflects the muscle's intermediate position between the anterior and medial compartments.

4. Blood Supply

The pectineus receives its blood supply from the medial circumflex femoral artery, the obturator artery, and the femoral artery. The venous drainage follows the corresponding veins into the femoral vein and the profunda femoris vein.

5. Actions

The pectineus acts at the hip joint to produce flexion, adduction, and medial rotation of the thigh. It is a synergist to the iliopsoas in hip flexion and to the adductor group in adduction. Its role in medial rotation distinguishes it from some of the larger adductors.

6. Clinical Relevance

Pectineus strains are a common cause of groin pain in athletes, particularly in sports involving rapid changes of direction. The muscle is a key surgical landmark: its tendinous insertion on the pectineal line is used in the medial approach to the hip and in pelvic osteotomies. The pectineus forms part of the floor of the femoral triangle; a psoas abscess or haematoma tracking into the femoral triangle may displace the femoral vessels anteriorly over the pectineus. The dual innervation of the pectineus means that the muscle is partially spared in isolated femoral or obturator nerve palsies, and therefore its function does not reliably test either nerve individually.

Summary

Summary of Pectineus

The pectineus is a flat, quadrangular muscle that flexes, adducts, and medially rotates the hip. It originates from the pecten pubis and inserts on the pectineal line of the femur. It is innervated by both the femoral and obturator nerves, and receives blood from the medial circumflex femoral and obturator arteries. It forms part of the floor of the femoral triangle and is clinically relevant in groin strains and as a surgical landmark.