UC San Diego UC San Diego Previously Published Works Title Pes Anserinus: Anatomy and Pathology of Native and Harvested Tendons. Permalink https://escholarship.org/uc/item/1wf3c2bd Journal AJR. American journal of roentgenology, 213(5) ISSN 0361-803X Authors Curtis, Brian R Huang, Brady K Pathria, Mini N et al. Publication Date 2019-11-01 DOI 10.2214/ajr.19.21315 Peer reviewed eScholarship.org Powered by the California Digital Library University of California Musculoskeletal Imaging • Review Curtis et al. Pes Anserinus Musculoskeletal Imaging Review Pes Anserinus: Anatomy and Pathology of Native and Harvested Tendons Brian R. Curtis1,2 OBJECTIVE. The purpose of this article is to review the anatomy and pathology of the Brady K. Huang1 pes anserinus to increase the accuracy of imaging interpretation of findings affecting these Mini N. Pathria1 medial knee structures. Donald L. Resnick1 CONCLUSION. The pes anserinus, consisting of the conjoined tendons of the sartorius, Edward Smitaman1 gracilis, and semitendinosus muscles and their insertions at the medial aspect of the knee, is of- ten neglected during imaging assessment. Common pathologic conditions affecting the pes an- Curtis BR, Huang BK, Pathria MN, Resnick DL, serinus include overuse, acute trauma, iatrogenic disorders, and tumors and tumorlike lesions. Smitaman E es anserinus, Latin for “goose primarily of the superficial medial collateral foot,” describes the gross ap- ligament (MCL), which has fibers that blend P pearance of the insertion of the with the posterior oblique ligament and in conjoined distal sartorius, graci- turn fuse with layer 3, the deepest. Layer 3 lis, and semitendinosus tendons at the an- consists of the joint capsule, which includes teromedial aspect of the tibia. This medial the meniscotibial and meniscofemoral com- region of the knee has complex anatomic fea- ponents of the deep MCL. Regarding the pes tures that include not only these myotendi- anserinus, the distal sartorius muscle and nous structures and their entheses, but near- tendon are enveloped by the crural fascia by ligaments, fascia, nerves, and bursae. (layer 1), and the deeper gracilis and semi- Abnormalities of these structures may be re- tendinosus tendons are situated between lay- lated to overuse, inflammation, acute or re- ers 1 and 2 (Figs. 1A and 1B). Keywords: anterior cruciate ligament, gracilis, petitive trauma, surgery, and tumors or tu- neotendon, pes anserinus, reconstruction, sartorius, morlike lesions. Despite the complex Pes Anserinus Muscles semitendinosus anatomy and range of pathologic conditions The sartorius, Latin for “tailor” in refer- doi.org/10.2214/AJR.19.21315 that can be encountered in this region, the lit- ence to the cross-legged sitting position of erature devoted to the pes anserinus is sparse, garment makers, is a strap muscle innervat- Received February 15, 2019; accepted after revision focusing primarily on pes anserinus bursitis ed by the femoral nerve. It originates from May 21, 2019. and complications related to tendon harvest- the anterior-superior iliac spine, traverses the The opinions and assertions contained herein are the ing for anterior cruciate ligament (ACL) re- anterior compartment of the thigh from the private views of the authors and are not to be construed construction [1–10]. The purpose of this ar- lateral to medial direction as it courses in- as official or as representing the views of the U.S. ticle is to review the normal anatomy and feriorly, and inserts into the proximomedial Department of Veterans Affairs. range of pathologic conditions that can affect tibia. It is the longest muscle in the human the pes anserinus. body, but is fairly weak, acting only as a syn- Based on a presentation at the ARRS 2018 Annual Meeting, Washington, DC. ergistic muscle. Anatomy of the Pes Anserinus and Gracilis, Latin for “slender,” describes the 1Division of Musculoskeletal Radiology, University of Nearby Structures long, thin appearance of this strap muscle, California San Diego Health System, San Diego, CA. As originally described by Warren and which is innervated by the obturator nerve. 2Veterans Health Administration National Teleradiology Marshall [1, 2], the soft-tissue structures at It originates from the ischiopubic ramus and Downloaded from www.ajronline.org by Mini Pathria on 08/20/19 IP address 76.176.203.32. Copyright ARRS. For personal use only; all rights reserved Program, 1001 Sneath Ln, San Bruno, CA 94066. Address the medial knee can be divided into three an- courses inferiorly within the medial com- correspondence to B. R. Curtis ([email protected]). atomic layers. Layer 1, the most superficial partment of the thigh toward the knee, where layer, consists of the medial portion of the it runs and inserts just posterior to the sarto- AJR 2019; 213:1–10 thin crural fascia, which is a circumferen- rius muscle and tendon. 0361–803X/19/2135–1 tial structure that encircles the knee and in- The semitendinosus, named after its long cludes the medial patellar retinaculum, pop- insertional tendon that forms in the midthigh, © American Roentgen Ray Society liteal fascia, and fascia lata. Layer 2 consists is a fusiform pennate muscle innervated by AJR:213, November 2019 1 Curtis et al. the sciatic nerve. It originates from the ischi- ly extends proximally to the joint line (i.e., Disorders of the Pes Anserinus al tuberosity as a conjoined tendon in com- proximal articular surfaces of the medial and Disorders of the pes anserinus can be di- mon with the long head of the biceps femoris lateral tibial condyles), though it can extend vided into four broad categories: overuse, muscle and courses inferiorly in the posteri- as far as 20 mm above this line, as seen in ap- acute trauma, iatrogenic causes, and tumors or compartment of the thigh behind the semi- proximately 24% of specimens [7]. Addition- and tumorlike lesions (Table 1). membranosus muscle toward the knee, where al bursae situated along the medial aspect of it inserts posterior to the gracilis tendon. the knee include the semimembranosus and Overuse MCL bursae. The semimembranosus bursa Pes anserinus bursitis—Pes anserinus Pes Anserinus Tendons is posterior and superior to the pes anserinus bursitis is mostly related to overuse by ac- The anatomy of the pes anserinus is in- bursa, whereas the MCL bursa is between tive persons, typically runners. It has also tricate. The sartorius tendon remains inti- the deep and superficial fibers of the MCL at been associated with inflammatory arthri- mate with the crural fascia (layer 1), and the the central third of the knee. Although bursi- tides, diabetes mellitus, obesity, injury, and gracilis and semitendinosus tendons are lo- tis of these bursae can coexist with pes anse- friction from nearby osteophytes or exosto- cated on the deep surface of this superfi- rinus bursal fluid, the bursae are not known ses. The diagnosis of pes anserinus bursi- cial layer over the medial tibia. Important- to communicate with each other [11–15]. tis is usually established by the characteris- ly, the pes anserinus lies superficial to and tic clinical finding of pain localized to the inserts proximal and anterior to the superfi- Saphenous Nerve and Its Branches proximomedial tibia, but in some instances cial MCL (layer 2) [1–3]. The pes anserinus The saphenous nerve arises from the fem- the clinical picture is unclear, and advanced tendon complex consistently inserts into the oral nerve at the femoral triangle and then imaging is requested. proximomedial tibia 42 ± 7 mm below the courses distally through the adductor canal, With ultrasound, the pes anserinus bur- level of the tibial plateau, distal and medial crosses medially to the femoral vessels, ex- sa can be identified in its usual position to the tibial tuberosity [9, 10]. Each tendon tends toward the knee between the sartorius (i.e., between the pes tendons and the tibia) attaches in a nearly linear arrangement—the and gracilis tendons (Fig. 1C), and continues in approximately 67% of volunteers with- sartorius proximally, followed by the gracilis inferiorly within the medial subcutaneous fat out symptoms, between the pes tendons and and semitendinosus tendons (average tendon of the leg along with the greater saphenous MCL in 21%, and between the constituents of widths of 8.0, 8.4, and 11.3 mm, respective- vein. Just above the knee joint, the saphenous the pes anserinus in 8% [20]. At MRI, fluid is ly)—at the lateral edge of the pes anserinus nerve bifurcates into infrapatellar and sarto- seen within the bursa deep to the pes anseri- bursa [3]. These tendons can have individ- rial branches. The infrapatellar branch can nus tendons and superficial to the superficial ual insertions; however, accessory tendons pierce the sartorius muscle or course anterior MCL [21]. Classically, distention of the bursa and fascial bands are often present that have or posterior to it. It provides sensory innerva- occurs near the pes anserinus insertion, dis- independent osseous and soft-tissue attach- tion to the medial infrapatellar region (Fig. tal and medial to the tibial tuberosity (Fig. 2), ments. The semitendinosus tendon, the most 1D). Its subcutaneous location and horizontal and fluid may invaginate deep to the superfi- morphologically variable tendon of the pes course along the medial knee place it at risk cial MCL. The pes anserinus bursa can also anserinus, can have as many as three tendi- of injury during surgical procedures involv- extend above the joint line [7]. nous insertions and various soft-tissue exten- ing the pes anserinus, such as graft harvest- Pes anserinus bursitis is typically man- sions, including a constant band that attaches ing for ACL reconstruction. Some authors aged conservatively with rest and oral an- to the gastrocnemius fascia [4–10] (Fig. 1B). [10, 16, 17] have suggested that an oblique tiinflammatory agents. In refractory cases, incision paralleling this branch, rather than aspiration of the bursal contents and local in- Pes Anserinus Bursa a perpendicular vertical incision, may lower jection of anesthetics or corticosteroids may The synovium-lined pes anserinus bursa is the risk of nerve injury.