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Functions and anatomy of the adductor magnus muscle shown with 3D model animation.
Hi everyone! This is Joao from Kenhub, and on this tutorial, we will cover the functions of the adductor magnus muscle, which is the muscle now isolated on the screen. The adductor magnus muscle is a composite muscle. This means that it has more than one part, each with a different innervation.
Before we go any further, I would like to explain to you about this white-colored, non-textured portion of the muscle right here that you can see here adjoining the proximal part of the adductor magnus. Now, this is a variable structure known as the adductor minimus muscle, and by variable, I mean that it varies in shape, size, and also attachment points.
Although the adductor minimus is often physically attached to then the adductor magnus, it is often considered as a separate muscle, hence, why we blocked it out here just for clarity. If you would like to find out more about the adductor minimus, however, you will find another 3D muscle function video on our website specifically dedicated to it.
As you can see on the screen, the adductor magnus muscle has a triangular fan-like shape. It consists of two parts – an adductor pubofemoral portion and a hamstring ischiocondylar portion. And it is the largest and most powerful muscle of the adductor group. It has a gap in the distal attachment of the adductor portion known as the adductor hiatus. This allows for the passage of major vessels from the thigh to the leg and can be a useful tool in identifying the muscle.
The adductor magnus muscle is located in the lower limb in the medial compartment of the thigh, and is the most posteriorly located of the adductor muscles. The medial compartment can be found on the inside of your thigh closest to the midline of your body.
The adductor muscles are in general innervated by the obturator nerve, however, the adductor magnus muscle is a little different. As we mentioned before, the adductor magnus muscle is a composite muscle, and if you remember, this means that the muscle has multiple parts which receive innervation from different sources.
The adductor portion of the adductor magnus muscle is innervated by branches of the posterior division of the obturator nerve as expected since almost all adductor muscles are innervated by then the obturator nerve. But there is also another part of the muscle – the hamstring part. This portion of the muscle receives its innervation from the tibial part of the sciatic nerve.
Just a quick note here useful for practical exams are the root values of these nerves. The root values of the branches of the posterior division of the obturator nerve are L2, L3, and L4, and in this case, the root value of the tibial part of the sciatic nerve is L4.
There are also differences in the attachments of the portions of the adductor magnus muscle. The adductor part of the muscle has its proximal attachment or origin on the inferior ramus of the pubis and ramus of the ischium. It attaches distally or inserts via a fibrous tissue called an aponeurosis along the entire length of the linea aspera of the femur. This results in the triangular fan-shape of the muscle that I talked about before. The distal insertion continues onto the medial supracondylar ridge of the femur.
The hamstring part of the adductor muscle has its proximal attachment or origin on the ischial tuberosity on the ischium. Now the distal attachment or insertion of the hamstring portion of the adductor magnus muscle is located on the adductor tubercle on the medial side of the femur.
In terms of the actions of the adductor magnus muscle, it acts on the hip joint. The adductor magnus muscle belongs to the adductor muscle group and has both an adductor and hamstring portion as we mentioned previously. This means there are a number of different influences which dictate the actions this muscle undertakes.
We will consider the composite muscle as a whole first. The main action of the adductor magnus in conjunction with the other muscles of the adductor group is unsurprisingly to adduct the thigh. If we begin in the anatomical position, then rotate slightly to get a good view of the muscle, we can see that the action of adduction occurs when the thigh is pulled medially and moves towards and past the midline of the body or median plane. When acting as part of the adductor muscle group, the adductor magnus muscle is instrumental in this action.
Adduction is an action which occurs when turning a corner while riding a motorcycle or bicycle, for example, since the thighs are pressed together or when kicking with the medial side of the foot, say, in soccer or football.
Next, we will consider the adductor portion of the adductor magnus muscle. This part of the muscle helps to flex the thigh when the hip is extended. You can see the hip joint on the screen now. Flexion occurs when the distance between the torso and the anterior thigh decreases. This is the action that you can see now. Flexion of the hip is required when you are, for example, running.
And finally, we will consider the hamstring portion of the adductor magnus muscle. This part of the muscle helps to extend the thigh both in particular when the hip is flexed. If we begin with the hip in a flexed position as you can see now on the screen, then extension of the hip occurs when the distance between the torso and the anterior thigh increases. Starting from the anatomical position then rotating slightly, we can see another example of the extension movement. This action is also required when you are, again, running.
The hamstring part of the adductor magnus muscle is also involved in extension of the thigh when the hip is extended. The adductor magnus muscle, however, is only a minor contributor to this movement as it is produced more so by the hamstrings and gluteal muscles.
Rotation of the hip is not a primary function of the adductor magnus muscle, but it is listed as an accessory function in some anatomy books, so should be mentioned in this tutorial. So, rotation of the hip by the adductor muscles is a contentious issue for which there are numerous research papers available for further reading. However, the general consensus is that the adductor magnus muscle does assist in primarily lateral rotation of the thigh at the hip joint.
You can see this action on the screen now with the adductor magnus highlighted throughout the action.
So, in summary, the adductor magnus muscle acts on the hip joint and acting as part of the adductor group of muscles is responsible for adduction of the thigh. This is an action involved in kicking with the medial side of the foot. The adductor portion of the muscle is responsible for flexion of the thigh when the hip is extended, and the hamstring portion of the muscle is responsible for extension of the thigh when the hip is flexed. These actions are required when you run, for example. The rotational actions of the adductor magnus are a bit debatable, but the consensus is that it assists in lateral rotation.
If you are interested, there is a lot more research available out there if you want to do further reading about this topic.
This, everyone, concludes our video tutorial on the functions of the adductor magnus muscle. Thanks for watching and I will see you on the next tutorial.