The pes anserinus aids knee stability by helping the medial ligament resist valgus forces. Under the conjoined tendons lies the pes anserine bursa, a sac which provides smooth movement of the conjoined hamstring tendons over the medial collateral ligament. Visually, these conjoined tendons form a structure reminiscent of a gooseвЂ™s webbed foot and were named from the Latin roots, pes for foot and anserinus for goose. Each of these three muscles is innervated by a different nerve: the femoral, obturator and tibial nerves respectively. The pes anserinus (PA) вЂ“ also known as pes anserine or the вЂgooseвЂ™s footвЂ™ вЂ“ refers to a conjoined insertion of the sartorius, gracilis and semitendinosus muscles along the proximal medial aspect of the tibia ( see figure 1). Because these injuries are comparatively rare, missed diagnosis is common and can result in unnecessary knee surgery. However, in athletes with vigorous and repetitive hamstring use, there is another possibility вЂ“ pes anserinus injury. When medial knee pain presents, there are several possible causes, including an injury to the medial ligament, medial cartilage/meniscus, or medial tibial stress fracture. Knee injuries are prevalent in athletes due to the loads transmitted through the knee joint during sport. The name comes from the Latin for goose's foot, in view of the similarity of the structure to the webbed foot of the bird.XVIII Pan American Games вЂ“ Lima 2019 вЂ“ Roller Speed Skating REUTERS/Susana Vera Some of the accessory bands of the semitendinosus muscle emerge up to 12 cm proximal to the pes anserinus insertion 3. The accessory bands usually insert on the gastrocnemius or popliteus fascia 3. Accessory bands from the sartorius and/or gracilis tendon are less frequent 3,4. In respect to the accessory bands, the majority seem to emerge from the semitendinosus tendon 3,4. The variant anatomy is of particular clinical importance since the pes anserinus serves a harvest site for tendon grafts e.g. This bursa can become inflamed and symptomatic: pes anserinus bursitis. The pes anserinus bursaВ lies between the pes anserinus tendons and the more deeply located semimembranosus tendon at the level of the knee joint. The sartorius tendon insertion usually has a short tendon insertion, the gracilis tendon and its accessory bands show most often (ca.80%) a band-shaped attachment, whereas the semitendinosus tendon and its accessory bands are characterized by a fan-shaped insertion (ca. The type of insertion can be classified into a short, band-shaped and fan-shaped, with fan-shaped defined as the insertion being two times the width of the tendon and band-shaped being less than two times the tendon width 3.

The pes anserinus inserts on the medial side of the tibial tuberosity below or distal to the tibial tuberosity with significant variant anatomy 3,4, comprising mostly different accessory tendinous bands appearing from the different tendons. These tendons insert onto the anteromedial proximal tibia approximately 4 cm distal to the tibial plateau 2.

See hereВ for mnemonics for remembering the three conjoined tendons that make up the pes anserinus.

The three tendons that form the pes anserinus (from anterior to posterior) are 1,2: The term 'pes anserinus' may also be used to describe the branching point of the facial nerve (CN-VII)В within the parotid gland.

Pes anatomy