Semimembranosus muscle

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Semimembranosus muscle
Semimembranosus muscle.PNG
Muscles of the gluteal and posterior femoral regions (semimembranosus labeled at bottom left)
Origin Ischial tuberosity
Insertion Medial condyle of tibia
Artery Profunda femoris and gluteal arteries
Nerve Tibial part of sciatic nerve
(L5, S1 and S2)
Actions Extension of hip and flexion of knee
Antagonist Quadriceps muscle and Tensor fasciae latae
Latin Musculus semimembranosus
TA98 A04.7.02.036
TA2 2642
FMA 22438
Anatomical terms of muscle

The semimembranosus muscle ( /ˌsɛmiˌmɛmbrəˈnsəs/ ) is the most medial of the three hamstring muscles in the thigh. It is so named because it has a flat tendon of origin. It lies posteromedially in the thigh, deep to the semitendinosus muscle. It extends the hip joint and flexes the knee joint.



cross-section of thigh semimembranosus labelled bottom right Gray432 color.png
cross-section of thigh semimembranosus labelled bottom right

The semimembranosus muscle, so called from its membranous tendon of origin, is situated at the back and medial side of the thigh. It is wider, flatter, and deeper than the semitendinosus (with which it shares very close insertion and attachment points). [1] The muscle overlaps the upper part of the popliteal vessels.


The semimembranosus muscle originates by a thick tendon from the superolateral aspect of the ischial tuberosity. [1] It arises above and medial to the biceps femoris muscle and semitendinosus muscle. The tendon of origin expands into an aponeurosis, which covers the upper part of the anterior surface of the muscle; from this aponeurosis, muscular fibers arise, and converge to another aponeurosis which covers the lower part of the posterior surface of the muscle and contracts into the tendon of insertion.


The semimembranosus muscle inserts on the:

The tendon of insertion gives off certain fibrous expansions: one, of considerable size, passes upward and laterally to be inserted into the posterior lateral condyle of the femur, forming part of the oblique popliteal ligament of the knee-joint; a second is continued downward to the fascia which covers the popliteus muscle; while a few fibers join the medial collateral ligament of the joint and the fascia of the leg.

Nerve supply

The semimembranosus is innervated by the tibial part of the sciatic nerve. [1] The sciatic nerve consists of the anterior divisions of ventral nerve roots from L4 through S3. These nerve roots are part of the larger nerve network–the sacral plexus. [2] The tibial part of the sciatic nerve is also responsible for innervation of semitendinosus and the long head of biceps femoris.


The semimembranosus muscle may be reduced or absent, or double, arising mainly from the sacrotuberous ligament and giving a slip to the femur or adductor magnus.


The semimembranosus muscle extends (straightens) the hip joint. It also flexes (bends) the knee joint. [1]

It also helps to medially rotate the knee: the tibia medially rotates on the femur when the knee is flexed. It medially rotates the femur when the hip is extended. The muscle can also aid in counteracting the forward bending at the hip joint. [2]

Clinical significance

The semitendinosus muscle may be dry needled. [1]

Additional images

See also

Related Research Articles

Human leg Lower extremity or limb of the human body (foot, lower leg, thigh and hip)

The human leg, in the general word sense, is the entire lower limb of the human body, including the foot, thigh and even the hip or gluteal region. However, the definition in human anatomy refers only to the section of the lower limb extending from the knee to the ankle, also known as the crus or, especially in non-technical use, the shank. Legs are used for standing, and all forms of locomotion including recreational such as dancing, and constitute a significant portion of a person's mass. Female legs generally have greater hip anteversion and tibiofemoral angles, but shorter femur and tibial lengths than those in males.

Knee Region around the kneecap

In humans and other primates, the knee joins the thigh with the leg and consists of two joints: one between the femur and tibia, and one between the femur and patella. It is the largest joint in the human body. The knee is a modified hinge joint, which permits flexion and extension as well as slight internal and external rotation. The knee is vulnerable to injury and to the development of osteoarthritis.

In human anatomy, a hamstring is any one of the three posterior thigh muscles in between the hip and the knee. The hamstrings are quite susceptible to injury.

Thigh Area between the pelvis and the knee; upper leg

In human anatomy, the thigh is the area between the hip (pelvis) and the knee. Anatomically, it is part of the lower limb.

Tibia Long bone of the lower leg

The tibia, also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates, and it connects the knee with the ankle bones. The tibia is found on the medial side of the leg next to the fibula and closer to the median plane or centre-line. The tibia is connected to the fibula by the interosseous membrane of the leg, forming a type of fibrous joint called a syndesmosis with very little movement. The tibia is named for the flute tibia. It is the second largest bone in the human body next to the femur. The leg bones are the strongest long bones as they support the rest of the body.

Popliteal artery Continuation of the femoral artery that supplies the lower leg

The popliteal artery is a deeply placed continuation of the femoral artery opening in the distal portion of the adductor magnus muscle. It courses through the popliteal fossa and ends at the lower border of the popliteus muscle, where it branches into the anterior and posterior tibial arteries.

Gastrocnemius muscle Calf muscle

The gastrocnemius muscle is a superficial two-headed muscle that is in the back part of the lower leg of humans. It runs from its two heads just above the knee to the heel, a three joint muscle. The muscle is named via Latin, from Greek γαστήρ (gaster) 'belly' or 'stomach' and κνήμη (knḗmē) 'leg', meaning 'stomach of leg'.

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.

The biceps femoris is a muscle of the thigh located to the posterior, or back. As its name implies, it has two parts, one of which forms part of the hamstrings muscle group.

Adductor magnus muscle Muscle in the thigh

The adductor magnus is a large triangular muscle, situated on the medial side of the thigh.

Gracilis muscle Most superficial muscle on the medial side of the thigh

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

Semitendinosus muscle One of Hamstring muscles: Posterior compartment of the thigh

The semitendinosus is a long superficial muscle in the back of the thigh. It is so named because it has a very long tendon of insertion. It lies posteromedially in the thigh, superficial to the semimembranosus.

Popliteus muscle Muscle responsible for unlocking the knees during walking

The popliteus muscle in the leg is used for unlocking the knees when walking, by laterally rotating the femur on the tibia during the closed chain portion of the gait cycle. In open chain movements, the popliteus muscle medially rotates the tibia on the femur. It is also used when sitting down and standing up. It is the only muscle in the posterior (back) compartment of the lower leg that acts just on the knee and not on the ankle. The gastrocnemius muscle acts on both joints.

Popliteal fossa

The popliteal fossa is a shallow depression located at the back of the knee joint. The bones of the popliteal fossa are the femur and the tibia. Like other flexion surfaces of large joints, it is an area where blood vessels and nerves pass relatively superficially, and with an increased number of lymph nodes.

Fascia lata Deep fascia of the thigh

The fascia lata is the deep fascia of the thigh. It encloses the thigh muscles and forms the outer limit of the fascial compartments of thigh, which are internally separated by intermuscular septa. The fascia lata is thickened at its lateral side where it forms the iliotibial tract, a structure that runs to the tibia and serves as a site of muscle attachment.

Lateral condyle of tibia

The lateral condyle is the lateral portion of the upper extremity of tibia.

Oblique popliteal ligament

The oblique popliteal ligament is a broad, flat, fibrous band, formed of fasciculi separated from one another by apertures for the passage of vessels and nerves.

Posterior compartment of thigh One of the fascial compartments that contains the knee flexors and hip extensors

The posterior compartment of the thigh is one of the fascial compartments that contains the knee flexors and hip extensors known as the hamstring muscles, as well as vascular and nervous elements, particularly the sciatic nerve.

Knee bursae

The knee bursae are the fluid-filled sacs and synovial pockets that surround and sometimes communicate with the knee joint cavity. The bursae are thin-walled, and filled with synovial fluid. They represent the weak point of the joint, but also provide enlargements to the joint space. They can be grouped into either communicating and non-communicating bursae or, after their location – frontal, lateral, or medial.

Deep fascia of leg Forms a complete investment to the muscles

The deep fascia of leg, or crural fascia forms a complete investment to the muscles, and is fused with the periosteum over the subcutaneous surfaces of the bones.


This article incorporates text in the public domain from page 479 of the 20th edition of Gray's Anatomy (1918)

  1. 1 2 3 4 5 6 7 8 9 Sandalcidi, Dawn; Dommerholt, Jan (2013-01-01), Dommerholt, Jan; Fernández-de-las-Peñas, César (eds.), "10 - Deep dry needling of the hip, pelvis and thigh muscles", Trigger Point Dry Needling, Oxford: Churchill Livingstone, pp. 133–150, doi:10.1016/b978-0-7020-4601-8.00010-4, ISBN   978-0-7020-4601-8 , retrieved 2021-03-01
  2. 1 2 Saladin, Kenneth S. Anatomy & Physiology: the unity of form and function. 5th ed. New York: McGraw-Hill, 2010. Print.