External Oblique Aponeurosis

aponeurosis musculi obliqui externi abdominis

The external oblique aponeurosis is the broad flat tendinous expansion of the external oblique muscle that forms the anterior abdominal wall below a line from the ninth costal cartilage to the ASIS. It is composed of parallel fibre bundles running obliquely downward and medially, fusing at the midline into the linea alba. Its inferior free border forms the inguinal ligament (Poupart ligament) from the ASIS to the pubic tubercle. The superficial inguinal ring is a triangular opening in the aponeurosis.

Region: Abdomen

Biomechanics

Function & Actions

Forms the anterior layer of the rectus sheath above the arcuate line, the inguinal ligament as its inferior free edge, the anterior wall of the inguinal canal, and the superficial inguinal ring through which the spermatic cord exits.

Clinical Relevance

Clinical Notes

The external oblique aponeurosis defines inguinal hernia anatomy: the superficial ring is the external opening of the inguinal canal in the aponeurosis, and the inguinal ligament is its inferior border. Open inguinal hernia repair (Lichtenstein) uses the inguinal ligament border of the aponeurosis as the fixation point for the posterior mesh placement. The aponeurosis is split longitudinally in the Pfannenstiel and transverse abdominal incisions. In sports hernia (athletic pubalgia), tears in the external oblique aponeurosis near the pubic attachment produce chronic groin pain.

Pathology

Common Injuries & Conditions

Athletic Pubalgia from External Oblique Aponeurosis Tear

Repetitive kicking and trunk rotation in footballers tears the external oblique aponeurosis at its pubic attachment, producing chronic inguinal-adductor groin pain reproduced by resisted sit-up and adductor squeeze; MRI demonstrates the aponeurotic tear and pubic edema, with physiotherapy as first-line and surgical repair for refractory cases.