Muscular anatomy of the pes anserine
The pes anserine is composed of the:
LaPrade et al (2009) found each individual pes anserine tendon was attached in an almost linear fashion at the lateral edge of the pes anserine bursa. The sartorius tendon attaches more proximally, followed by the gracilis tendon and then the semitendinosus tendon.
Insertion: (1) joins to the pes anserine tendon below the tibial tuberosity. (2) Below and medial to the medial tibial tuberosity. (3) Deep fascia of the crus. (Dziedzic et al 2013).
Action (Dziedzic et al 2013):
- Initialises hip and knee flexion from the phase of full extension.
- Weak external rotator and abductor of the hip joint.
- Rotates the tibia and fibula internally with the knee joint flexed.
Origin: pubis, inferior pubic ramus, ischial ramus.
Insertion: upper part of the medial surface of the tibia.
Additional attachments: deep fascia of the lower leg and medial head of the gastrocnemius.
Actions: adducts, flexes and medially rotates the leg. When the foot is fixed the gracilis rotates the femur and pelvis laterally on the tibia.
Origin: ischial tuberosity, joint tendon of the biceps femoris and an aponeurosis connecting these two muscles.
Insertion: upper medial surface of the tibia behind the sartorius and distal to the gracilis. At its termination it is united to the gracilis tendon.
Additional attachments: deep fascia of the leg, gracilis, sartorius (Lee et al 2014), medial head of gastrocnemius and biceps femoris.
- Hip extension.
- Knee flexion.
- With the hip extended an internal rotator of the thigh.
Pes anserine bursa
The pes anserine bursa is located at the upper medial aspect of the tibia, at the insertion of the conjoined tendon of the pes anserine muscles. LaPrade et al (2009) found each individual pes anserine tendon was attached in an almost linear fashion at the lateral edge of the pes anserine bursa. The sartorius tendon attaches more proximally, followed by the gracilis tendon and then the semitendinosus tendon most distally. They also found attachments of the superficial medial collateral ligament to the pes anserine bursa.
The bursa separates the pes anserine tendons from the distal portion of the tibial collateral ligament and the bony surface of the medial tibial condyle. It does not communicate with the knee joint.
The shape of the anserine bursa is of an irregular circular. Lee et al (2014) found its boundaries to be:
Superior: the proximal line of the tibia (around the level of the tibial plateau), and sometimes above this.
Medial: follows the line of the sartorius muscle.
Inferior: 16mm from the inferomedial point of the tibial tuberosity and in relation to the pes anserine tendon.
Sometimes the infrapatellar nerve (from the saphenous nerve) lies near the bursa. Hemler et al (1991) presented a case of a patient with symptoms of medial tibial stress syndrome cured by an injection of the pes anserine bursa. They attributed this to an entrapment neuropathy of the saphenous nerve from a pes anserine bursitis.
Fascial layers of the medial knee
Wymenga et al (2006) identified three layers of the fascia in the medial knee:
Layer I: superficial fascia
The superficial fascia is subcutaneous. It blends with the pes anserine and tibial periosteum distally, it covers the sartorius and quadriceps proximally, the retinaculum anteriorly, and forms the deep crural fascia posteriorly.
The superficial portion of layer I adheres to the sartorius. The deep portion of layer I adheres to the gracilis and semitendinosus tendons.
Layer II: superficial medial collateral ligament
The superficial medial collateral ligament extends from the femoral epicondyle to the anteromedial tibial crest 5–7 cm below the joint line. LaPrade (2009) found a majority of the distal attachments of the superficial medial collateral ligament to be to the semimembranosus and pes anserine bursa rather than the tibia.
Posteriorly these fibres are continuous with the oblique fibres of layer III although this was disputed by LaPrade (2009) who found no clear connection.
Anterior to the femoral attachment these fibres are continuous with the medial patellofemoral ligament.
Tuncay et al (2007) found the semitendinosus and gastrocnemius tendons to lie between layer I and II.
Just as the superficial portion of layer I adheres to the sartorius, the deep portion of layer I adheres to the gracilis and semitendinosus tendons. Tuncay et al (2007) found two fascial bands associated with the semitendinosus:
- Dense 3–4-cm band around the gracilis and semitendinosus tendons approximately 8–10 cm proximal to their tendon insertion.
- Fascial band originating from the semitendinosus and extending to the gastrocnemius fascia.
Layer III: the true capsular layer and mid-third medial capsular ligament (deep medial collateral ligament)
Layer III thickens and forms the deep medial collateral ligament as a thickening of the medial joint capsule.
The deep medial collateral ligament (layer III) separates the superficial medial collateral ligament (layer II) from the medial meniscus.
The deep medial collateral ligament extends from the medial femoral condyle to the meniscus and from the meniscus to the tibia.
Proximally the deep medial collateral ligament attachment merges into the superficial medial collateral ligament fibres, but sometimes it has a distinct attachment 0.5 cm distally.
The meniscotibial attachment of the deep medial collateral ligament is clearly separated from the superficial medial collateral ligament but blends with it posteriorly.
Anterior to the superficial medial collateral ligament layer III is thin and loose blending with layer I into the retinaculum.
Conjoint attachments of layers II and III
The conjoined tissue of layers II and III forms the posteromedial capsule
A condensation of fibres within the posteromedial capsule forms the posterior oblique ligament. This ligament is an important stabiliser of the medial side of the knee.
The femoral attachment of the posteromedial capsule is located at the adductor tubercle.
The posteromedial capsule is augmented by:
- Semimembranosus tendon: inserts into the posteromedial tibia just below the joint line. It has various extensions into the posteromedial capsule and the posterior capsule.
- Adductor Magnus tendon: LaPrade et al (2009) found the distal-medial aspect of the adductor magnus tendon had a thick fascial expansion, which fanned out posteromedially and attached to the medial gastrocnemius tendon, the capsular arm of the posterior oblique ligament and the posteromedial capsule.
- Gastrocnemius: as well as a thick fascial attachment to the adductor magnus the medial gastrocnemius has a thin fascial band extending to the capsular arm of the posterior oblique ligament (LaPrade et al 2009).
The fascial band from semitendinosus to gastrocnemius: the critical point of hamstring harvesting An anatomical study of 23 cadavers (2007) Ibrahim Tuncay, Hudaverdi Kucuker, Ibrahim Uzun and Nazim Karalezl
The Anatomy of the Medial Part of the Knee (2009). Robert F. LaPrade, Anders Hauge Engebretsen, Thuan V. Ly, Steinar Johansen, Fred A. Wentorf, Lars Engebretsen
Surgical anatomy of the medial collateral ligament and the posteromedial capsule of the knee (2006) Ate B Wymenga Sint Maartenskliniek, Jan-Jaap Kats, Jan G M Kooloos
Anatomy and Biomechanics of the Medial Side of the Knee and Their Surgical Implications (2015) Matthew D. LaPrade, Mitchell I. Kennedy, Coen A. Wijdicks, and Robert F. LaPrade
Anatomy of sartorius muscle (2013). D. Dziedzic, U. Bogacka, B. Ciszek
Surgical anatomy of the medial collateral ligament and the posteromedial capsule of the knee (2006). A. B. Wymenga J. J. Kats J. Kooloos B. Hillen
Pes anserinus and anserine bursa: anatomical study (2014). Je-Hun Lee, Kyung-Jin Kim, Young-Gil Jeong, Nam Seob Lee, Seung Yun Han, Chang Gug Lee, Kyung-Yong Kim, and Seung-Ho Han
Saphenous Nerve Entrapment Caused by Pes Anserine Bursitis Mimicking Stress Fracture of the Tibia (1991) Douglas E. Hemler, Wendy K. Ward, Kent W. Karstetter, Phillip M. Bryant
The fascial band from semitendinosus to gastrocnemius: the critical point of hamstring harvesting An anatomical study of 23 cadavers (2007). Ibrahim Tuncay, Hudaverdi Kucuker, Ibrahim Uzun & Nazim Karalezli