Hip and Lower Back: The Basics

The first part of this piece will give you a basic understanding of how the muscles in the lower back and hip work. The second part is a little more detailed for those that want to better understand the anatomy.

The Mechanics

Can you imagine stacking a bunch of blocks on top of soft cushions and expecting the whole thing to be stable?  Sounds crazy, right? If you were going to do it, you’d need to tie the blocks down on all 4 sides to make the structure rigid. Yet, what if you needed to also able to move? Things would get complicated very fast. You’d need a lot more wires, pullies and a system to control the whole thing. Some of the wires would have to go tight at the same time others went loose.

The fascinating thing is, this is close to how your lower back, or lumbar spine, actually does work. A series of blocks stacked on cushions, or bones stacked on top of discs. The spine has many different roles:

• Protect the spinal cord and nerves that send messages to every part of your body
• Allow movement so that you can bend, lift, twist, sit and walk.
• Transfer and disperse force while you are bending, lifting, twisting walking etc

And do you know what? It does this far more elegantly and reliably than any guy-wire or pulley system ever could!

How it Works

How it does this is actually quite remarkable, and something that we all take for granted every day. The bones provide the protection to the spinal cord. And the muscles provide the stability and movement. But, the muscles of the spine work different than the way most people understand them to function.

The muscles of your spine (spinal erectors) are not designed to pull on bones to make them move. Not like the muscles of your arms or legs do. They are designed differently. The angles are wrong. The attachments are too weak, limiting the amount of movement each spinal bone has. But, as a group, the spinal erectors run from the base of your skull to the top of your hips.

Their job is to contract and stiffen the spine. By being on each side of the back bones (vertebra) they can lock the spine in place and provide rigid stability. So, working as a group they provide the support needed to keep blocks stacked and stable on cushions while you move!

The Strength is in the Hips!

So, if you’re supposed to have a stiff back when you bend, where does the movement come from? Your hips. You need a strong back that can stiffen on command and strong, mobile hips that can lower you down and bring you back up. It is the glut max and hamstrings that help you bend down and bring you up, not your back. Treatment and rehab should be designed with this in mind. Our treatment focuses on improving the motion of your hips. We focus on the ability of the back to contract and stiffen. Our rehab exercises teach the back to stiffen and build the strength of the hips and legs. Then, you can use the right muscles when you bend over. Using the wrong muscles can cause you trouble. Time to tighten up the saggy bums!

A More Detailed Explanation

The role of the muscles of the erector spinae – multifidus, longissimus and iliocostalis – is spinal stability. It is not to extend or move the individual joints that they cross over. The individual muscles are in the wrong position with the wrong angles of force to extend the joint efficiently. They are too weak. They have small tendons that attach to the thin bone of the spinous process and transverse process. Muscles that pull to flex and extend the joints they surround are much bigger. Those have strong tendons and strong attachments, think biceps and triceps for example.

If you look at the position of these muscles, they are encased by bone on one side (the spinous and transverse processes) and a thick fascia on the other side. This makes them like two column that run either side of the spine. When the erector spinae contract, then don’t do so to pull the vertebra, but to stiffen and thicken. Because they are encased, this changes the column from soft to rigid, locking the spine in place. Arguably, the QL and Psoas muscles also play a similar role around the more anterior aspects of the vertebral body.

Flexion comes from the hips, not the spine. The gluts, hamstring and adductor magnus are all large and powerful muscles. Or at least they should be. Though, in a lot of people they are not strong enough. A weak posterior chain will lead to the muscles of the back working in a way that they shouldn’t. When muscles work in a role they are not designed for, injuries happen.

Andrew Knowles is a chiropractor with over 12 years’ experience. He has worked in the UK and around Australia. And learned from some of the best minds in the musculoskeletal industry. He brings a unique approach to treating problems of the lumbar spine and hips.