Origins, insertions, innervation and functions of the adductors of the thigh.
Hello, hello, everyone! This is Joao from Kenhub, and welcome to another tutorial where, this time, I'm going to be talking about another group of muscles known as the adductors of the thigh. Now, as I mentioned, yes, this is a group of muscles that you find on your thigh. And right now, I have here an image showing you the anterior view of your thigh. And I am going to remove right now the anterior thigh muscles, right now, so you can expose and see the thigh adductors.
Now, depending on how you look at these muscles, you can talk about in terms of functions, which we are right now, because we call them thigh adductors, but you can also call them hip adductors depending also whether you’re looking at them working on or producing functions on the hip joint. But you can also talk about in terms… define this group of muscles in terms of location. And if we were to do so, we would say that these are medial thigh muscles.
So these are the medial thigh muscles because if you remember well from other tutorials that we have here at Kenhub, there are also the anterior thigh muscles, and you have a posterior group, so posterior thigh muscles, and eventually, this one that we’re going to be talking about today. And as you can clearly see here on this image, the thigh adductors range from the lower pelvic bone to the femur. So they go all the way from the pelvic bone to the femur and also to the knee region. And these muscles shape the surface anatomy of the medial thigh.
The first thing that I want to talk about is in terms of innervation. As you can clearly see now highlighted in green, this is the nerve that is going to be responsible for most of the adductors, so most of the innervation of the adductors. And this one is the obturator nerves which arises from the lumbar plexus—and you can clearly see here on this image—and reaches the adductors through the obturator canal.
There are two muscles that belong to the thigh adductors that have what is called as double innervations, and we’re going to check that out later on on this tutorial.
Another important part of this tutorial would be to mention before we go into details, but I would like to just briefly mention the different functions associated to this group of muscles, the thigh adductors. And as the name suggests, this muscle or these muscles are going to be involved in adduction. They’re going to be also contributing to other functions which include external rotation, internal rotation, flexion, and extension.
Now, the hip adductors are particularly used when crossing… when you cross your legs, and overall, they play an important role in balancing your pelvis during standing and also when you walk. And a very important situation when you need your adductions is when you go ice skating during winter. The slippery ice lets your legs glide laterally, so you need your adductors to pull them back medially so you don’t accidentally split your legs. And this might really hurt. So thanks to your adductors, you are covered.
Before I go on and talk about the different muscles that belong to the thigh adductors, I want to list them. And these are the pectineus, the adductor magnus, we’re going to be talking about the adductor longus, and if we have a longus, we might as well have a brevis, and the minimus, the adductor minimus, and we’re going to finalize this tutorial talking about another muscle that belongs to this group known as the gracilis.
Let’s start off with the very first one here on our list. Now, seen highlighted in green, this muscle is the pectineus. And the pectineus runs from the superior, so in terms of origin, from the superior pubic ramus, which you can clearly see here on this image. This is the origin point for this muscle and a point known as the iliopubic eminence. Then this muscle is going to go all the way to the femur to insert on what is known to be as the pectineal line and the linia aspera of the femur. So right here, right about in this area, this is where the pectineus is going to be inserting.
Now, another thing to add here is that I mentioned before there are a couple of muscles that will be or will have double innervation. And the pectineus is clearly this case. So in terms of additional innervation, we’re going to see that this muscle is going to be innervated not only by the obturator nerve like we saw before, but also this nerve seen here, highlighted on the image on the right side. This is known as the femoral nerve.
Also, I would like to add a few words on the different functions associated to this muscle. And what it does, this muscle is responsible for adduction, of course, as we mentioned, of the hip, and also flexion, as you can see here represented by both of these arrows.
Now, we’re going to move on to the second muscle on our list. This one seen here highlighted in green. This is known as the adductor magnus, and it does deserve its name because it’s one of the largest muscles in your body and the largest one of the group that we’re talking about on this tutorial. And it’s so large that we can actually divide it into two parts. And these parts are what is known as a muscular or adductor part. And the other one is the tendinous or hamstring part.
Now, let’s have a look at the different origin points for this large muscle, and we need to remember three. One is the inferior pubic ramus. The other one is the ischial ramus which will serve as the origin point for the muscular part, while the tendinous part is going to come from the ischial tuberosity. And you can see the origin points here combined for the adductor magnus.
Now, this muscle goes all the way from the different hip bones to the femur to then insert at the linea aspera. So there is this fleshy insertion as you can see here that is going to be inserting on the linea aspera. And another insertion point that we call the tendinous point or tendinous insertion as you can see here that is going to go all the way to the medial condyle of the femur.
In terms of innervation, if you remember well, this is one other muscle that is going to have double innervations. Because it’s so large, it definitely deserves another nerve. And in terms of innervation, we’re going to be seeing the obturator nerve as we talked about in the beginning innervating the adductor magnus. But the tendinous part of the adductor magnus is going to be also supplied by this nerve that you see here on the screen, highlighted in green. And if you guess it well, yes, this is the tibial nerve.
Now, moving on from the innervation of the adductor magnus, we’re going to talking about the different functions associated to this muscle. There are few that you need to remember, because since this is a large muscle, it’s going to be inserting on different points as we’ve seen before. And every time it contracts, it will cause different types of movements.
The first one is an obvious one that associated to the name. This is adduction. But this muscle will also cause external rotation and also flexion of the thigh at the hip joint. And in addition to that, the tendinous insertion of the adductor magnus will also produce internal rotation and extension of the hip joint. That way, depending on which part of the muscle is contracting, it will result in either a flexion or extension of the hip.
Now, we’re going to move on to the next one on our list, this long muscle seen here, highlighted in green. And yes, I spoiled it already. This is a long muscle, and we’re going to be calling it the adductor longus. And the adductor longus is going to be originating from two parts that we need to remember here. The first one is the superior pubic ramus, and the other part is the pubic symphysis. And you can clearly see here on this image, pubic symphysis, which is partially serving as the origin point for the longus, the adductor longus. And also the superior pubic ramus is serving as an origin point for this muscle.
Now, as a long muscle, it is going to go all the way to find its insertion on the femur on the linea aspera, which will serve as other muscles that we’ve seen before. The linea aspera is also going to be serving as insertion point for the adductor longus.
I wanted to add here an important point for your notes before the next exam, so you have something extra to know about this muscle, is that, distally, the adductor longus is going to form an aponeurosis which then extends to the vastus medialis muscle, and this is called the vastoadductorial membrane.
So the next part that we’re going to be talking about is related to the different functions of the adductor longus. There are two that you need to remember. One is already shown on the name of the muscle, and that is adduction. And the other one is going to be flexion, so flexion of the thigh at the hip joint.
Let’s move on to the next muscle on our list, this one seen here, highlighted in green. This is known as the adductor brevis. So if you had a longus, you need to have a short one, the brevis. And in terms of origin points, you need to remember one, and that is the inferior pubic ramus which you can also see here. This is going to serve as the origin point for the adductor brevis.
And in terms of insertion point, we’re going to be talking about or seeing that this muscle is going all the way to another area that we’ve been talking about, another insertion point that we talked about for other muscles, other thigh adductors. If you remember, yes, on the femur the linea aspera which will serve then as the insertion point for this muscle.
Next stop is going to be the different functions associated to the adductor brevis. And also, you need to remember just a few. The first one is on the name, the adduction. The other one is going to be external rotation of the thigh. And the other one is going to be flexion of the thigh at the hip joint.
It’s time for us to move on to next muscle on our list, this one seen here, highlighted in green, known as the adductor minimus. The adductor minimus describes the inconstant cranial separation of the adductor magnus, which is found in many but not all people. So this is an important point to remember.
Let’s talk about the origin point for the adductor minimus. And you just need to remember one that the inferior pubic ramus, as you can see here in this image, is going to be serving as the origin point for the adductor minimus.
While the insertion point for this muscle is going to be also one and the same as many others that we talked about, the linea aspera on the femur is going to be serving as insertion point for the adductor minimus.
Moving on to the different functions associated to the adductor minimus, there are two that you need to remember. Two functions, one is on the name, the adduction and the other one: flexion of the thigh.
The last muscle on our list is this one here, this long, long muscle known as the gracilis. And the gracilis runs from the inferior border of the pubic symphysis and goes all the way to insert, as you can see here, quite long, and it’s going to go all the way to insert on the superficial pes anserinus.
Important thing to mention about the gracilis is that its tendon is easy to palpate in the inguinal region together with another muscle or the tendon of another muscle, the adductor longus muscle.
The next topic here on this tutorial is going to be the different functions associated to the gracilis. Now, being the only two-joint adductor, the gracilis muscle moves the knee joint as well, where its contraction causes, then, flexion and internal rotation of the knee represent by these two arrows as you can see here. The other functions associated to the gracilis would be then adduction and flexion of the hip joint just like the rest of the thigh adductor muscles.
Now, I also wanted to make a point here on this tutorial about an insertion point that we talked about before, the pes anserinus. That is an insertion point for different muscles. And this is a popular exam question, so I wanted to highlight here on this slide. And the pes anserinus is a roughly goose foot-shaped insertion point for the following three muscles. And these are the gracilis, as we saw before, the semitendinosus muscle, and the sartorius. So all these three muscles are going to go all the way to the medial proximal surface of the tibia to then insert on this insertion point that is called the pes anserinus.
Another important fact to mention here is that, sometimes, the insertion of the semimebranosus is referred to as the pes anserinus profundus or the deep pes anserinus.
And before I end the tutorial, I wanted to do a review on the different functions of the thigh adductors, starting off with the adduction and flexion that was seen on all thigh adductors—so remember this. And another one was external rotation that was seen on these three muscles, the pectineus, the adductor brevis, and adductor magnus. We also saw an internal rotation. The tendinous insertion of the adductor magnus and the gracilis are responsible for internal rotation of the thigh. Another function we saw here on our muscles was extension that was seen on the tendinous insertion of the adductor magnus.