Pes Anserine: Anatomical Definition and Clinical Significance
The pes anserinus (Latin for "goose's foot") is the conjoined tendinous insertion of three muscles—sartorius, gracilis, and semitendinosus—that attach to the anteromedial aspect of the proximal tibia, forming a layered supportive structure that stabilizes the medial side of the knee joint. 1, 2
Anatomical Structure
The pes anserinus consists of three distinct muscle tendons that converge and insert on the medial tibia:
- The sartorius tendon forms the most superficial layer with a longitudinal fibrous bundle on its surface 1
- The gracilis tendon lies in the middle layer, covered by an aponeurotic membrane with a deep longitudinal fibrous bundle 1
- The semitendinosus tendon forms the deepest layer, also with an aponeurotic membrane that fuses with surrounding fascial structures 1
The gracilis and semitendinosus tendons typically fuse approximately 3.18 cm proximal to their tibial insertion and are firmly adherent to the overlying sartorius tendon. 3
The upper border of the gracilis tendon is located an average of 5.5 cm distal to the anteromedial joint line of the knee. 3
Functional Role
These three tendons, along with their associated aponeurotic membranes and fascial connections, function as a complex tensor fasciae cruris mechanism that provides critical medial stabilization of the knee joint, particularly during upright posture and dynamic movement. 1
The pes anserinus receives additional stabilizing contributions from a small tendinous expansion of the semimembranosus muscle that fuses with the semitendinosus aponeurotic membrane, tibial collateral ligament, and the fascia covering the medial head of the gastrocnemius. 1
Anatomical Variations
Anatomical variations of the pes anserinus occur in approximately 48% of individuals, ranging from fascial loops connecting the sartorius tendon to the medial collateral ligament to separate tendon slips inserting independently into the tibia or crural fascia. 3
Clinical Pathology
Common pathologic conditions affecting the pes anserinus include:
- Pes anserinus syndrome (anserine bursitis): painful inflammation of the pes anserinus bursa, more common in overweight adult females but rare in pediatric populations 2, 4
- Overuse injuries and acute trauma affecting the tendinous insertions 2
- Avulsion fractures: rarely occur but can be associated with recurrent lateral patellar dislocations causing chronic stress on medial knee stabilizers 5
- Mechanical irritation from osteochondromas: particularly those located at the medial-posterior edge of the proximal tibia, which can cause pes anserinus syndrome even when small (0.5-2.5 cm), requiring surgical resection for symptom resolution 4
Surgical Relevance
The pes anserinus tendons, particularly the gracilis and semitendinosus, are commonly harvested for knee ligament reconstruction procedures, making precise anatomical knowledge critical for safe and efficient dissection. 3
An inverted L subperiosteal incision beginning at the tibial crest provides optimal exposure for harvesting these tendons while accounting for the anatomical variations present in nearly half of patients. 3