Which muscles form the pes anserinus?
Three muscle tendons contribute to the formation of this anatomical structure:
- Sartorius muscle (m. sartorius) is the longest muscle in the body. It originates from the anterior superior iliac spine, runs obliquely downward and medially, transitioning to the anterior and medial surface of the knee.
- Gracilis muscle (m. gracilis) originates from the inferior ramus of the pubis and the pubic symphysis.
- Semitendinosus muscle (m. semitendinosus) is a slender, long muscle on the posterior aspect of the thigh. It originates from the ischial tuberosity (tuber ischiadicum). In the middle third of the thigh, its muscle belly transitions into a long tendon; posterior to the medial femoral condyle, the tendon contributes to the pes anserinus.
Topography and insertion site
The tendons of the sartorius, gracilis, and semitendinosus muscles share a common insertion site on the medial surface of the tibia, in the area of its tuberosity (tuberositas tibiae). Some of the superficial fibers of the semitendinosus tendon blend into the fascia of the leg.
The anserine bursa (bursa anserina) is located near the insertion site. For the sartorius muscle, 2 to 3 subtendinous bursae are also frequently described here.
Blood supply and innervation of the muscle complex
The muscles of the pes anserinus have distinct innervation and blood supply:
- M. sartorius: Innervated by the femoral nerve (n. femoralis, LII–LIII). Supplied with blood by the lateral femoral circumflex artery (a. circumflexa femoris lateralis), descending genicular artery (a. genus suprema), and branches of the femoral artery.
- M. gracilis: Innervated by the anterior branch of the obturator nerve (n. obturatorius, LII–LIII). Blood supply is provided by the external pudendal artery (a. pudenda externa), obturator artery (a. obturatoria), and deep artery of the thigh (a. profunda femoris).
- M. semitendinosus: Innervated by the tibial nerve (n. tibialis, LIV–LV; S1). Supplied with blood by perforating arteries (aa. perforantes), which are branches of the deep artery of the thigh.
Functions and clinical significance
The muscles whose tendons form the pes anserinus perform the following actions:
- Flex the leg at the knee joint.
- Perform medial rotation, i.e., inward rotation of the leg.
- Participate in stabilizing the medial side of the knee.
From a clinical perspective, this area is important due to its association with medial knee pain: the adjacent bursa anserina is cited as a frequent cause of such pain.
Do not confuse: other "pes anserinus" structures in anatomy
In topographical anatomy of the head, there are structures with similar names. "Minor goose foot" (pes anserinus minor) is formed by the superior labial branches of the infraorbital nerve. In addition, the "goose foot" mnemonic is used to describe the projection of the facial nerve branches: the motor branches of the facial nerve diverge in a fan-like manner from a point inferior and anterior to the tragus of the ear.
The "goose's foot" / hand projection mnemonic is used to memorize the course of the facial nerve branches. If you place your hand on the lateral surface of the face so that the thumb (digit I) vertically crosses the middle of the zygomatic arch, the fingers indicate the directions of the branches: I — temporal, II — zygomatic, III — buccal, IV — marginal mandibular, V — cervical.
Class and exam questions
Which muscles form the pes anserinus in the lower limb?
It is formed by the tendons of three muscles: the sartorius (m. sartorius), gracilis (m. gracilis), and semitendinosus (m. semitendinosus).
Where exactly does this structure insert?
The tendons insert onto the medial surface of the tibia, in the area of the tibial tuberosity (tuberositas tibiae).
Why might the knee hurt in the area of the pes anserinus?
The bursa anserina, located near the insertion of these tendons, is a frequent cause of medial knee pain.
What is the pes anserinus minor?
This is a structure formed by the superior labial branches of the infraorbital nerve (n. infraorbitalis) after its exit through the infraorbital foramen.
What else to study on this topic
- Sartorius muscle (m. sartorius)
- Semitendinosus muscle (m. semitendinosus)
- Gracilis muscle (m. gracilis)
- Infraorbital nerve (n. infraorbitalis)
- Facial nerve (n. facialis)
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