The pes anserinus is the insertion of the conjoined tendons of three muscles onto the anteromedial (front and inside) surface of the proximal extremity of the tibia

Upper extremity of tibia

The upper extremity of the tibia is large, and expanded into two eminences, the medial condyle and lateral condyle.-Facets:The superior articular surface presents two smooth articular facets....

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Anatomy

The three muscles are (from anterior to posterior):

• sartorius
  Sartorius muscle
  The Sartorius muscle – the longest muscle in the human body – is a long thin muscle that runs down the length of the thigh. Its upper portion forms the lateral border of the femoral triangle.-Origin and insertion:...
  
  
• gracilis
  Gracilis muscle
  The gracilis is the most superficial muscle on the medial side of the thigh. It is thin and flattened, broad above, narrow and tapering below.-Origin and insertion:...
  
  
• semitendinosus

The conjoined tendon lies superficial to the tibial insertion of the medial collateral ligament

Medial collateral ligament

The medial collateral ligament of the knee is one of the four major ligaments of the knee. It is on the medial side of the knee joint in humans and other primates. It is also known as the tibial collateral ligament, or abbreviated as the MCL.- Structure :It is a broad, flat, membranous band,...

 (MCL) of the knee.

Mnemonic

A good mnemonic to remember the muscles which contribute tendons to this conjoined tendon and the innervations of these muscles is SGT FOT (sergeant FOT).

S- Sartorius G- Gracilis T- semiTendinosus (from medial to lateral)

F- femoral nerve

Femoral nerve

The femoral nerve, the largest branch of the lumbar plexus, arises from the dorsal divisions of the ventral rami of the second, third, and fourth lumbar nerves...

 O- obturator nerve

Obturator nerve

The obturator nerve in human anatomy arises from the ventral divisions of the second, third, and fourth lumbar nerves; the branch from the third is the largest, while that from the second is often very small.-Path:...

 T- tibial nerve

Tibial nerve

The tibial nerve is a branch of the sciatic nerve. The tibial nerve passes through the popliteal fossa to pass below the arch of soleus.In the popliteal fossa the nerve gives off branches to gastrocnemius, popliteus, soleus and plantaris muscles, an articular branch to the knee joint, and a...

 (one of the two component nerves of the sciatic nerve [the other being the common fibular (or common peroneal) nerve

Common fibular nerve

The common fibular nerve , about one-half the size of the tibial nerve, is derived from the dorsal branches of the fourth and fifth lumbar and the first and second sacral nerves.It descends obliquely along the lateral side of the popliteal fossa to the head of the fibula,...

]. The sciatic nerve

Sciatic nerve

The sciatic nerve is a large nerve fiber in humans and other animals. It begins in the lower back and runs through the buttock and down the lower limb...

 itself cannot technically innervate anything because it is merely the designation for the common sheath

Wiktionary

Wiktionary is a multilingual, web-based project to create a free content dictionary, available in 158 languages...

 that encases the tibial and common fibular nerves.)

Notice the order of the muscles (S, G, T) follows the order of the innervating nerves which correspond to those muscles (F, O, T)

Another useful mnemonic is

Say Grace before Tea, or just plain old S G T.

Elucidating the insertion of the three muscles from anterior to posterior

Sartorius - Gracilis - semiTendinosus

Clinical significance

It is a cause of chronic knee pain and weakness ("pes anserine bursitis

Pes Anserine Bursitis

Pes anserine bursitis is an inflammatory condition of the medial knee at the bursa of the pes anserinus.- Pathology :The pes anserinus is the anatomic term used to identify the insertion of the conjoined tendons Sartorius, Gracilis, and Semitendinosus into the anteromedial proximal tibia...

"). Pes bursitis is a condition in which the medial portion of the knee is inflamed. If the bursa underlying the tendons of the sartorius

Sartorius muscle

The Sartorius muscle – the longest muscle in the human body – is a long thin muscle that runs down the length of the thigh. Its upper portion forms the lateral border of the femoral triangle.-Origin and insertion:...

, gracilis

Gracilis muscle

The gracilis is the most superficial muscle on the medial side of the thigh. It is thin and flattened, broad above, narrow and tapering below.-Origin and insertion:...

, and semitendinosus gets irritated from overuse or injury a person can develop this ailment. This condition usually occurs in athletes from overuse. This pathology is characterized by pain, swelling, and tenderness.

The semitendinosus tendon can be used in certain techniques for reconstruction of the anterior cruciate ligament

Anterior cruciate ligament

The anterior cruciate ligament is a cruciate ligament which is one of the four major ligaments of the human knee. In the quadruped stifle , based on its anatomical position, it is referred to as the cranial cruciate ligament.The ACL originates from deep within the notch of the distal femur...

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External links

• Description at rad.washington.edu