• Nick Aunkst

5 Minute Reads: Understand the Hip Flexors

Updated: May 30, 2018

When you spend your days working with pain, biomechanics, anatomy and movement, it’s easy to forget that others don’t spend their days that way. A recent conversation led me to remember this important fact: we don’t always understand our own bodies. The body is complicated structure! Wound deeply within all the complications of structure and function, there’s a beauty that we oftentimes forget is important to comprehend. As cliche as it may sound, you only get one body to take you through this life. With that being said, it’s important to understand the components of it and how you can get the most out of it.

That recent conversation mentioned earlier was in relation to hip flexor anatomy. “Tight hip flexors” are a common topic of conversation today, catching the blame for many musculoskeletal complaints (and sometimes, rightfully so). With all of this blame being passed along to the dreaded “tight hip flexor” let's shed some light on the actual region itself, including the anatomy, movement descriptions and their importance to musculoskeletal health.

Here’s a quick overview. Flexion is a mechanistic position that decreases the angle of a joint. Hip flexion itself is the action of drawing your knee/leg towards your midsection. It can be performed sitting/standing/lying supine/passive/active/etc. On average, active/passive hip flexion should reach an estimated 120 degrees. This will obviously vary person-to-person, depending on size and shape of various regions. But in this world we like to standardize things, so there you go.

Pulling knee towards chest = hip flexion.

The hip flexor group is crowded and complicated. Many times only one or two muscles are thought to play a role in hip flexion, this isn’t true. The hip flexor group is actually comprised of 10 different players, that’s enough to fill a starting baseball roster (even in the AL, where you play with a DH!) There are major players and minor players in the group, but all-in-all they all function in some sort of synergy which is important to human mechanics. Here’s a list for those of you taking notes:

  • Psoas major, Psoas minor, Iliacus ,Rectus femoris, Tensor Fascia Lata, Adductor Brevis, Adductor Longus, Gracilis, Pectineus, and Sartorius

We’ve used this phrase many times before, but it still reigns true: your body is a smart beast. It knows where to divert attention. With the dedication of 10 different muscles to be involved in hip flexion, you can see that we’re created with an emphasis on the action. Here’s a visualization:

For the sake of time (considering this is only a “5 minute read”...) we’re going to touch on a few of the muscles today, and then a few more at a later time. Let's talk about the big guys today, the ones who normally catch most of the blame, and why.

Psoas Major/Psoas Minor/Iliacus: We’re going to talk about these three together, because separating them is tough and can become redundant for the sake of conversation. The psoas major/minor muscle originates on the front/lateral portion of vertebral bodies of the thoracolumbar and lumbar spine. This is deep inside the abdomen, below all the soft tissue structures of the digestive tract. The iliacus muscle lives within the pelvic basin, spanning a good majority of the anterior surface of the superior pelvis. All three of these muscles combine within the region to form a common tendon, that then inserts on a bony prominence called the “lesser trochanter”, which lives on the inside of your upper thigh, near the groin. When you want to flex your hip, this is one of the more powerful and prominent regions involved.

Rectus Femoris: Rectus Femoris can be easily overlooked, but it’s a critical player in hip flexion. It originates from the front of the hip, on a deep structure called the Anterior Inferior Iliac Spine (AIIS). It then travels down the middle of the thigh, meets up with three other muscles to form the quadriceps group, crosses the knee cap, and then inserts on another bony prominence called the Tibial Tuberosity. The rectus femoris is unique, in that it crosses two major joint lines (the hip and the knee). It helps to flex the hip, pulling it towards the chest, as well as extend (or straighten) the knee with the quadriceps group.

Now that we know a little more of the anatomy, what’s the importance of all of this? One common theme in our discussions is this: The body most commonly responds to the demands that are most commonly placed upon it. What kind of demands on you putting on your body? Do you spend more time with your hip flexed or extended? If you’re like most common Americans, you’re asking your hip flexors to remain statically flexed for most of the day. They’re going to remember that and it will become an all-to-familiar position.

This can sneakily present with symptoms over time in the lumbar spine and the pelvis, leading to misuse/disuse/overuse symptoms to occur (something we’ve touched on in prior discussion). Once the hip has become accustomed to it’s new demands (constant/static flexion), and then is asked to do something else, like extend or generate force, weird things begin to happen. Even something as simple as standing up from a chair can be a taxing experience. Leaning, twisting, and torquing into unique positions just to simply rise from a chair are not uncommon adaptations, and are not to be ignored.

The take home: the body most commonly responds to the demands that are most commonly placed upon it (that’s right, said it again). Don’t let the body get too comfortable being too comfortable. Let yourself get comfortable with the uncomfortable. This means, get up and move, stand, lean, lift and stretch throughout the day. When demands placed on the body are variable in nature throughout most of the day, your body doesn’t have enough time to create preconceived perceptions about it’s demands, therefore it’s more likely to be primed for anything life may throw it’s way.

Stay tuned for later discussions on "the other" hip flexors!





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