Logan Steele
The semimembranosus muscle is one of three hamstring muscles in the thigh, extending the hip joint and flexing the knee joint. It is wider, flatter, and deeper than the semitendinosus muscle, and it gets its name from its membranous tendon of origin. The semimembranosus muscle is susceptible to injuries, particularly in athletes, and these injuries can require a significant recovery period. This is due to the complex structure of the semimembranosus muscle, which has a unique architecture that may be classified as a pennate muscle. Pennate muscles are characterized by their resemblance to the shape of a feather, with muscle fibres attaching obliquely to a central tendon. This arrangement allows for increased force generation and a greater number of muscle fibres within the muscle. The semimembranosus muscle, with its specific structure and function, provides an interesting case study for understanding the role and importance of pennate muscles in the human body.
| Characteristics | Values |
|---|---|
| Definition | The semimembranosus muscle is the most medial of the three hamstring muscles in the thigh. |
| Location | The semimembranosus muscle is situated at the back and medial side of the thigh. |
| Functions | The semimembranosus muscle extends the hip joint, flexes the knee joint, and helps to medially rotate the knee. |
| Innervation | The semimembranosus muscle is innervated by the tibial part of the sciatic nerve. |
| Blood Supply | The popliteal, posterior tibial, and peroneal arteries supply blood to the semimembranosus muscle. |
| Pennate Muscle Characteristics | Pennate muscles resemble the shape of a feather, with muscle fibers attaching to a central tendon at an oblique angle. They can be further classified as unipennate, bipennate, or multipennate. |
| Unipennate Muscle | The extensor digitorum of the forearm is an example of a unipennate muscle, with fascicles located on one side of the tendon. |
| Bipennate Muscle | The rectus femurs is an example of a bipennate muscle, with fascicles on both sides of the tendon. |
| Multipennate Muscle | The deltoid muscle of the shoulder is an example of a multipennate muscle, with fascicles inserting on multiple tendons that converge towards a common tendon. |
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What You'll Learn
- The semimembranosus muscle is one of the three hamstring muscles in the thigh
- It extends the hip joint and flexes the knee joint
- The muscle is innervated by the tibial part of the sciatic nerve
- Semimembranosus musculotendinous injuries (SMMTI) are common in sports
- The muscle is wider, flatter, and deeper than the semitendinosus muscle
The semimembranosus muscle is one of the three hamstring muscles in the thigh
The semimembranosus muscle plays a crucial role in extending the hip joint and flexing the knee joint. Additionally, it helps in the medial rotation of the knee and femur. The muscle is innervated by the tibial part of the sciatic nerve, which consists of anterior divisions of ventral nerve roots from L4 through S3. This nerve network is known as the sacral plexus.
Injuries to the semimembranosus muscle can be challenging to treat and typically require a longer recovery time compared to other hamstring muscle injuries. The complex structure of the semimembranosus muscle, including its proximal tendon and its attachments, contributes to the varying recovery times and prognoses.
The semimembranosus muscle is not specifically mentioned as being a pennate muscle in the sources that come up in a search. However, pennate muscles are characterised by their feather-like structure, with muscle fibres attaching obliquely to a central tendon. They can be further classified into unipennate, bipennate, or multipennate muscles, depending on the arrangement of the fascicles. The semimembranosus muscle's structure, particularly the way its fibres attach to its tendon, may exhibit characteristics of pennate muscles, but this information is not explicitly provided in the sources.
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It extends the hip joint and flexes the knee joint
The semimembranosus muscle is one of four posterior thigh muscles that are responsible for extending the hip. The other three muscles that belong to the hip extensor group are semitendinosus, biceps femoris, and gluteus maximus. Collectively, semimembranosus, semitendinosus, and biceps femoris are referred to as the hamstring muscles. The semimembranosus is the most medial of the three hamstring muscles in the thigh. It is wider, flatter, and deeper than the semitendinosus, with which it shares very close insertion and attachment points.
The semimembranosus muscle extends (straightens) the hip joint and flexes (bends) the knee joint. It also helps to medially rotate the knee: the tibia medially rotates on the femur when the knee is flexed, and the femur when the hip is extended. The muscle can aid in counteracting forward bending at the hip joint. The semimembranosus is a relatively long muscle that spans the full length of the thigh, from the hip to the knee. It originates from a small facet on the rough superolateral surface of the ischial tuberosity. The tendon of semimembranosus appears at the level of the mid-thigh and continues caudally toward the point of insertion at the medial condyle of the tibia.
The semimembranosus muscle is innervated by the tibial part of the sciatic nerve, which consists of the anterior divisions of ventral nerve roots from L4 through S3. The tibial part of the sciatic nerve is also responsible for the innervation of the semitendinosus and the long head of the biceps femoris. The tendon of insertion of the semimembranosus gives off certain fibrous expansions: one 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 fibrous expansion continues downward to the fascia, which covers the popliteus muscle, while a few fibres join the medial collateral ligament of the joint and the fascia of the leg.
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 distal semimembranosus complex stabilizes the posterior capsule through the oblique popliteal ligament. On knee flexion during running, cutting, and pivoting, the capsular arm of the semimembranosus actively tightens the posterior oblique ligament, providing dynamic stability. The oblique popliteal ligament plays a significant role in preventing excessive external knee rotation and hyperextension, strengthening the stability of the knee.
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The muscle is innervated by the tibial part of the sciatic nerve
The semimembranosus muscle is one of three hamstring muscles in the thigh. It is wider, flatter, and deeper than the semitendinosus muscle, with which it shares close insertion and attachment points. The semimembranosus muscle is innervated by the tibial part of the sciatic nerve.
The sciatic nerve is the largest nerve in the human body. It originates in the lumbosacral region of the lower back and travels through the posterior aspect of the thigh, exiting the pelvis through the greater sciatic foramen. The nerve provides sensory and motor supply to the skin and muscles of the thigh, leg, and foot.
Just before reaching the popliteal fossa, the sciatic nerve divides into two branches: the tibial nerve and the common fibular (peroneal) nerve. The tibial nerve continues through the posterior compartment of the leg and foot, providing motor supply to muscles such as the gastrocnemius, soleus, and tibialis posterior.
The tibial nerve innervates the semimembranosus muscle, along with other hamstring muscles including the semitendinosus and the long head of the biceps femoris. These muscles are responsible for movements such as knee flexion and hip adduction.
The semimembranosus muscle, as a hamstring, plays a role in extending the hip joint and flexing the knee joint. It also helps to medially rotate the knee and counteract forward bending at the hip joint.
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Semimembranosus musculotendinous injuries (SMMTI) are common in sports
The semimembranosus muscle is the most medial of the three hamstring muscles in the thigh. It is wider, flatter, and deeper than the semitendinosus muscle, with which it shares very close insertion and attachment points. The semimembranosus muscle extends the hip joint and flexes the knee joint. It also helps to medially rotate the knee and femur.
The anatomical appearance of the hamstring muscle complex has been studied to better understand hamstring injury patterns and provide reference values for origin dimensions, muscle length, tendon length, and musculotendinous junction (MTJ) length. This includes the semimembranosus muscle, which has overlapping proximal and distal tendons with the long head of the biceps femoris muscle.
The recovery time for SMMTI can vary depending on the severity and location of the injury. Injuries involving the C region of the semimembranosus muscle typically require a longer recovery time, with a median of 49.1 days, compared to 27.8 days for injuries that do not involve the C region. Recurrent injuries are also common, prolonging the recovery process.
The treatment and rehabilitation of SMMTI aim to reduce the incidence of injuries and minimize the time away from sports. This includes understanding the anatomy and function of the semimembranosus muscle, as well as developing effective recovery protocols.
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The muscle is wider, flatter, and deeper than the semitendinosus muscle
The semimembranosus muscle is one of three hamstring muscles in the thigh. It is located at the back and medial side of the thigh, and is the most medial of the three hamstring muscles. The semimembranosus muscle is wider, flatter, and deeper than the semitendinosus muscle. It lies deep to the semitendinosus, and shares very close insertion and attachment points with it. The semimembranosus muscle extends the hip joint and flexes the knee joint. It also helps to medially rotate the knee and the femur.
The semimembranosus muscle is so named because it has a flat tendon of origin. It originates from the superolateral aspect of the ischial tuberosity, which is a small facet on the rough superolateral surface of the ischial tuberosity. The tendon of origin expands into an aponeurosis, which covers the upper part of the anterior surface of the muscle. From this aponeurosis, muscular fibres arise and converge to another aponeurosis. The semimembranosus muscle is a relatively long muscle that spans the full length of the thigh, from the hip to the knee.
The semitendinosus muscle, on the other hand, is a long, superficial muscle in the back of the thigh. It has a very long tendon of insertion, which is situated at the posterior and medial aspect of the thigh. The semitendinosus muscle lies between the semimembranosus and the biceps femoris muscles. These three muscles work collectively to flex the knee and extend the hip. The semitendinosus muscle is more superficial than the semimembranosus muscle, but because the semimembranosus is wider and flatter, it is still possible to palpate it directly.
The semimembranosus and semitendinosus muscles have similar functions, as they are both involved in extending the hip joint and flexing the knee joint. They also work together to medially rotate the tibia on the femur when the knee is flexed and to medially rotate the femur when the hip is extended. In addition, these muscles help to counteract forward bending at the hip joint. The semimembranosus and semitendinosus muscles are both innervated by the tibial part of the sciatic nerve.
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Frequently asked questions
The semimembranosus muscle is the most medial of the three hamstring muscles in the thigh. It extends the hip joint and flexes the knee joint.
Yes, the semimembranosus muscle is a pennate muscle. It has a complex structure and is susceptible to sports injuries.
Pennate muscles are one of the four basic shapes of muscles, along with fusiform, triangular, and rhomboidal. They resemble the shape of a feather, with muscle fibres attached obliquely to a central tendon.
