What Is A Hip Flexor?

(Originally posted on bcotoronto.com on Mar 7th, 2013)

One of our most important areas of movement is our hips. They are the main powerhouse movers while walking, working in conjunction with all the thigh muscles (which really involve the hip anyway). Everyone knows about the Gluteus muscles and even a few of the other big movers that make up our bums, but how many people can name what lies on the other side of the hip joint and helps us swing our leg forward?

This main mover is called the Iliopsoas (“Ill – eo – so – as”) muscle. It is made up of two muscle bodies coming together into a common tendon. They are the Iliacus and the Psoas muscles. The Iliacus muscle is a broad, flat muscle that attaches to the upper rim of the pelvis and sits on the inside surface of the pelvic bowl. This ends up making it look like a big fan and gives it the ability to pull on the femur (thigh bone) from many different angles.

The Iliacus MuscleThe Psoas muscle is actually two thick bands of muscle fibres (Psoas Major and Psoas Minor but we’re just going to refer to it as a single Psoas muscle for the ease of the description) that attach to the sides of the lumbar vertebrae. Its length and girth allows these two bands to pull on the femur with quite a bit of strength.

The Psoas MuscleAs the Iliopsoas, these two muscles work together to flex the hip joint and bring the leg forward. They are important in walking, running, sitting, swimming, and really any activity that requires the use of our legs. This grouping of “Hip Flexors” is one of the “Prime Movers” in our body which are responsible for making the large movements of our limbs and body as a whole.

This Hip Flexors are important for another reason too in this day and age. As a society, we sit much more than is good for us. The body, when in any posture for long periods of time, will adapt to that position as the default. This means that when we sit all day and our hips are flexed at a 90 degree angle, the Iliopsoas is shortened and our brains make that new length the default position for the muscle. So when we stand up again, we straighten out our hip joints but the Iliopsoas is no longer long enough and so this pulls our pelvis and lumbar spine forwards.

This creates an over extension of the lumbar spine which pushes the joints that the back of the spine together potentially causing low back pain and decreasing the size of the holes where nerves leave the lumbar spine potentially causing nerve pain that may travel into the leg. More commonly, the Iliopsoas will be a source of pain itself which can cause pain in the low back, pelvis, and genitals.

None of these situations are pleasant and there are two simple things that we can do to make sure they don’t happen; move and stretch. Get up from your desk every 15-20 minutes and stretch your hips and low back (and while you’re at it your shoulders and neck too) and walk around a little bit. This stimulation will keep the blood flowing through the body of the muscle and keep it limber and the appropriate length.

Remember. An ounce of prevention is worth a pound of cure.

Thanks for reading,
Dr. Ben


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