Leg muscles: which ones, anatomy and functions

Thanks to the release of the forelimbs and the visual advantage achieved in the upright position, the primitive ancestor of the human being greatly improved its ability to survive, allowing the use of tools and greater interaction with the environment around it.

The muscles of the legs are responsible for carrying the weight of the body when we are standing, providing stability and a wide capacity for movementto the human being. Thanks to the muscles of the legs we are able to walk, dance, run… An infinity of activities that define our day to day.

In this articlewe will talk about the muscles of the leg, emphasizing the functions they perform in the movement of the lower extremities. For this purpose, we will separate those muscles that intervene in the movement of the hips and knees, which are responsible for most of the mobility.

What do the leg muscles do?

There is alarge number of muscles in our lower extremities, which we can divide according to several parameters, such as their shape, location, nerves to which they are associated or the motor functions in which they participate. In this article we separate them according to the joints to which they are associated and the movement in which they intervene, to better understand the functions of the leg muscles.

To simplify their understanding, we will look mainly at the hip and knee joints, since they represent most of the muscle mass of the legs and are responsible for most of the mobility and stability functions of the legs.

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Hip-associated muscles

The hip is responsible for supporting much of the weight of the human body, with important functions in posture, organ protection, generation of blood cells, stability and mobility. To better understand the hip we can first look at the movements that mediate this joint and the muscles that participate in them.

There are mainly four types of muscles in the hip , which act to allow four different types of movement, increasing the range of motion and stability of this important structure of the musculoskeletal system. We would find:

1. Buttocks

In the group of the gluteus we find the  gluteus maximus  (the well-known  Gluteus maximus ), which is responsible for the extension of the hip, as well as the  gluteus medius , the  gluteus minimus  and the tensor of the fascia lata, which are responsible for the tasks abduction and internal rotation of the joint.

2. Adductors

In the group of adductor muscles of the leg we find those muscles that are in charge of  moving the femur towards the central line of the body . Among them we find five different muscles, which also participate in other functions of leg movement:

• Long adductor  of the thigh, which originates from the pubis and is broadly attached to the femur.
• Adductor magnus , the largest of the group, is involved in adduction, flexion, and extension of the thigh.
• Adductor brevis , a short muscle located under the adductor longus of the thigh.
• Obturator externus , is responsible for lateral rotation of the leg.
• The gracilis muscle , also known as the gracilis muscle, the most superficial muscle of the adductor group, has functions at both the hip and knee levels.

3. Lateral rotators

Within the muscles of the lateral rotator group we find muscles that are located deep within the leg muscles, which act to laterally rotate the leg from the knee, a movement in which the gluteus maximus and adductor magnus are also involved. They all originate in the pelvis and join the femur.

We would find in this group the following muscles:

• Piriformis , the most superior muscle within the lateral rotator group.
• Obturator internus , located on the inner wall of the pelvis
• The Gemini , two triangular muscles that are responsible for lateral rotation and abduction of the thigh.
• The quadratus femoris , a quadrate muscle made up of four distinct muscles. Its position is the lowest within the group of lateral rotators.

4. Iliopsoas

Within the group of Iliopsoas muscles we would find the iliacus and the psoas major, which combine to join the femur and perform their knee flexion functions.

• Psoas major , which originates near the midline of the body, adjacent to the spine.
• Iliacus , a large fan-shaped muscle located inside the pelvis, but anchored to the femur in combination with the psoas major.

Muscles associated with the knee

Another joint that plays a huge role in leg mobility is the knee . The muscles associated with the knee can be divided into three groups, which work in coordination to give the leg stability and range of motion, while also allowing for some special abilities of the knee.

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Among the leg muscles associated with the knee joint, we can highlight:

1. Popliteus

Muscles located in the posterior area of ​​the knee, which allow the femur and tibia to be unlocked when they have joined after full extension, again allowing the joint to flex.

2. Quadriceps

The quadriceps muscle group consists of the rectus femoris, the vastus lateralis, the vastus medius and the vastus intermedius, it is responsible for the extension functions of the leg from the knee joint.

3. Hamstrings

It is a group of three muscles (semitendinosus, semimembranous, and biceps femoris) located at the back of the knee. They are responsible for the flexion of the joint. They participate in the flexion movement, but also in the rotation movement in conjunction with other muscles such as the internal rectus and sartorius.

References

• Palastanga , N. , Field , D. , Soames , R. , & Gonzalez of Roman Field , P. (2007). Human anatomy and movement structure and function. Barcelona, ​​Spain: Paidotribo Publishing House.
• Platzer, W. (2004). Color atlas and textbook of human anatomy. Stuggart: Georg Thieme Verlag.