What do you need to know about the biomechanics of the hip?

In this article we are going to use a squat as an example, because that is the most common situation in a training session, where people might feel the decreased mobility of the hip.

Full range squat is a measurement of the ability of the hip to go through full range of motion. This should usually mean that an individual could access the joint ranges of motion available at the pelvis and femur. 


Just like the glenohumeral rhythm, the squat has three phases. In this example, I am using a hip flexion, which is the lowering (eccentric) phase of the squat.

Degrees 0-60 of Hip Flexion

When standing tall, the position is biased to the external rotation of the pelvis and the counternutation of the sacrum bone. These might sound “too anatomical”, but bare with me.

The counternutation of the Sacrum creates a need for the pelvic innominate bones to move forward into flexion, abduction, and external rotation relative to the sacrum so that the pelvis can maintain an even center of gravity over your foot as you descend into the squat.

If you look at what is going on under the hips, your feet are going to be in more of a supinated and externally rotated position.

Degrees 60-100 of Hip Flexion

60° to 90-100 degrees of hip flexion is where we begin to move into more of an internally rotated position of the pelvis. Now the sacrum is moving forward and that will cause a need for the pelvic innominate bones to rotate relatively backward (extension and internal rotation) to keep the weight over the foot without falling too far forward or backward.

Internal rotation is crucial for producing force through the hardest part of a squat. Now, if you are lacking proper internal rotation of the hips, you’ll often see them push their low back forward as compensation. This anterior pelvic tilt allows the femurs to internally rotate, but at the same time this can increase stress on the low back. Another common thing is, that you don’t have that internal rotation of the hips, you might drop without proper control into the bottom of a squat as a compensatory strategy to bypass internal rotation.

During this phase your feet are going to be in a more pronated position, which is required for achieving proper dorsiflexion of the ankle. This does not mean you have a flat feet, or that your knees would collaps in during squat. This is just the mechanical model of the hip and femur.

Degrees 100-120 of Hip Flexion

Under the parallel level, we start to orientate towards pelvic external rotation and the counternutation of the sacrum.

If you cannot get that motion to occur, you will probably go into a “butt-wink” where the pelvis as an entire unit roll backward and under. This is also a compensation strategy for the pelvis trying to get that counternutation.

People have different hip anatomy and there is about a +/- 15-degree difference between individuals when this counternutation is starting to happen again.

In many cases, this is more important than ankle mobility, which is what people usually say is the problem when someone can’t squat deep.

When the pelvis is moving towards external rotation, the foot is moving relatively into more supination and plantar flexion as well. Just like in the starting position. So contrary to what we usually think, we actually probably need less dorsiflexion in a deep squat.

How to Improve Squat Depth

So the home takeaway from here is that in order to get into a deep squat, you need that pelvic external rotation and sacral counternutation. This is hard to accomplish if you are stuck in an anterior pelvic tilt.

Because Anterior pelvic tilt is a position of hip flexion, we need to focus on movement drills that improve hip extension.

The role of posterior hip capsule

The hip capsule basically refers to the acetabulum or the socket in which the femur (leg bone) can rotate. For you to internally rotate the hip, we need the femoral head to push back within the acetabulum. When there is not enough internal rotation at the hip while producing force, there will be some level of compensation, such as lower back extension, knee valgus, or overpronation of the foot. If you find yourself having these “symptoms”, I recommend reading the article on Knee pain and Low back pain.

There is often also some capsular restriction, meaning the hip capsule itself is tight and needs releasing. Many people need some sort of posterior capsule stretch in order to maximize internal rotation, so let’s look at some nice drills for that too:

I hope this summary helped your understanding of the topic and helped you with your own biomechanical issues.

If you are interested in learning more, go check out our Movement Stick Coach – certification program, where you will learn tons of movements that you can do with the Stick.