Which Muscles Flex The Hip?! | 3D Anatomy Explained for Physios

Added: 2026-05-30

[00:00:01][music] >> Hey everyone, Khaled here. Welcome back to Clinical Physio. In today's video, we're going to be exploring the key muscles that flex the hip. If you like the anatomy that we're doing, please support us by smashing that like button, and otherwise, let's dive in with today's video on the muscles that flex the hip. So, first of all, let's talk through the four muscles because if you're a football or soccer fan, there's a really great mnemonic that you can remember to help you memorize the key muscles that flex the hip. And that little mnemonic is play it like Ronaldo does his famous Sue celebration when he scores. So, play it like Ronaldo Sue. Play stands for the psoas major muscle.

[00:00:55]It like stands for iliacus. I L stands for it like.

[00:01:01]Ronaldo, the R stands for rectus femoris, and then the Sue celebration is for the sartorius muscle. So, play it like Ronaldo Sue. Let's go through these muscles starting with of course the psoas major.

[00:01:18]So, the really interesting thing about psoas major, as you can see, is that it actually originates from the lumbar spine. We can see how it originates from the vertebral bodies of T12 to L4 with a little bit of an attachment to L5 as well here. It's also suggested to have a connection or an origin from the intervertebral discs between T12 and L4 as well, but nevertheless, the main thing to think about is that this muscle absolutely does originate from the lumbar spine, which means that it also has a secondary role in side flexion of the trunk as well.

[00:01:58]We can then see how it runs through the lumbar spine and then through the iliac region of the anterior hip before it goes in to insert into the lesser trochanter on the femur. And if we just rotate the model here, you can see the lesser trochanter here, which is where it inserts into.

[00:02:23]So, not only is this muscle a potent flexor of the hip, but it also is said to have a key role in stabilizing the anterior hip. Because of that position it has where it runs over the front of the hip joint, as we can see there, meaning that when the hip needs stabilizing anteriorly, it almost prevents the femur from moving too far forward. So, it really does stabilize the hip in that anterior position.

[00:02:49]So, the second muscle it like, which blends very much with the psoas major, is the iliacus muscle. So, let's look at this.

[00:02:58]So, this muscle originates from the iliac fossa. If we rotate the model here, we can see how it originates from this kind of internal rim of the ilium, which is the iliac fossa.

[00:03:12]And much like the psoas major, we can see how it runs through the iliac region in order to insert into the lesser trochanter. And what we can see here is how the two muscles actually blend together in order to insert onto that lesser trochanter of the femur that we can see just there. And that is why, effectively, you'll often hear these two muscles being referred to together as the iliopsoas, because we can see how their fibers and tendons effectively run together before inserting together into that lesser trochanter.

[00:03:50]So, psoas major and iliacus combining to be the iliopsoas.

[00:03:56]So, next we have the rectus femoris, the Ronaldo muscle as it were when we're thinking about that little mnemonic. So, of course we know that the rectus femoris is a really powerful knee extensor. However, because we can see that it originates from above the level of the hip joint, we can see that it also flexes the hip. And it has two origin points. It has a first origin point, also known as the straight head, that originates from the anterior inferior iliac spine of the pelvis.

[00:04:33]And we can see that it has a reflected head just here that breaks off slightly at an angle, which originates from the supraacetabular groove, or the supraacetabular tubercle, the groove or tubercle just superior to the acetabulum. So, remember because it crosses the hip joint, it also acts on the hip as a hip flexor.

[00:04:56]And we can see those two origin points there.

[00:04:59]And then, of course, it runs down the anterior thigh in order to insert into the quadriceps tendon, which then inserts into the patellar tendon, which then inserts into the tibial tuberosity, which makes it that knee extensor. But, the key thing to remember here, because of those origin points above the level of the hip, helping us remember that it's a hip flexor, too.

[00:05:23]And then, finally, we have the su for sartorius, one of the longest muscles, if not the longest muscle in the body.

[00:05:31]Certainly, it is in the lower limb.

[00:05:34]So, we can see that the sartorius originates from the anterior superior iliac spine. Do note that many people often get this wrong. They think that the rectus femoris originates from the ASIS, but it's actually the sartorius that originates from ASIS.

[00:05:50]And we can see how this muscle then famously runs diagonally across the anteromedial aspect of the thigh before it inserts medially into the proximal tibia at an area called the pes anserine region on the proximal medial tibia, helping us remember that it also has a role at the knee where it performs a role in knee flexion. But of course, when we think about the hip, we can see it clearly originates from above the level of the hip joint on the ASIS, helping us remember that it's a hip flexor as well.

[00:06:27]So, there you go. Play it like Ronaldo.

[00:06:29]So, those are your key muscles that flex the hip. Thank you so much for watching.

[00:06:34]If you've liked this video, please support us by smashing that like button.

[00:06:37]It's the number one thing you can do to help our channel. And remember, if you want more anatomy teaching on the hip, check out our membership platform, link in the description below, where you'll find the hip anatomy boot camp. Premium and annual members get full access to the hip anatomy boot camp as well as the knee anatomy boot camp, shoulder anatomy boot camp, elbow anatomy boot camp, all of our anatomy boot camps for the best anatomy teaching we can give you. Thank you so much for watching. Look forward to seeing you soon here on Clinical Physio.