Lower back and hip
The lumbar spine protects nerves while its disks and joints wear with age
Your lower back is a stack of bones cushioned by disks and wrapped in muscles and ligaments, with nerves running through the middle [1]. When one part wears down, it can crowd the others, which helps explain many common back problems [2].
Key points
- Almost every adult has low back pain at some point, and in most cases it goes away on its own within a few weeks [1].
- Disks cushion the spine, and with age they lose water, shrink and may tear or bulge [1][2].
- Worn facet joints, bone spurs and thickened ligaments can narrow the spinal canal and squeeze nerves [2].
- Numbness in the private area or loss of bladder or bowel control is a medical emergency [2].
The lumbar spine stacks vertebrae with disks and surrounds the spinal nerves
The spine is made of small bones called vertebrae, stacked on top of one another [1]. Muscles, ligaments, nerves and intervertebral disks are the other parts [1]. Each part has its own job.
| Part | What it does |
|---|---|
| Vertebrae | Small bones stacked on top of one another [1] |
| Intervertebral disks | Cushion the spine so it can tolerate movement and stress [1] |
| Facet joints | Small joints between each vertebra on the back of the spine [1] |
| Spinal canal | Holds the spinal cord and spinal nerves [2] |
| Nerves | Carry messages between your brain and your body from inside the spine [1] |
| Muscles and ligaments | Help stabilize the bones [1] |
Understanding these parts helps make sense of low back pain, which can be mild or severe, short-lived or long-lasting [1].
Intervertebral disks cushion the vertebrae and can tear or bulge
Disks act like cushions. When you are young they hold a lot of water, and as you age they lose water and get smaller [2]. A disk can also lose height or collapse [2].
A disk has a tough outer part called the annulus and a jelly-like center called the nucleus [1]. Small tears in the outer part sometimes occur with aging [1]. Some people with tears have no pain, while others have pain lasting weeks, months or longer [1]. It is not clear why some people hurt and others do not [1].
A disk herniates when its center pushes against the outer part, and in a very worn or injured disk it can squeeze all the way through [1]. If it bulges toward the spinal canal, it presses on sensitive spinal nerves and causes pain [1]. Because that pressure often lands on the nerve root leading to the leg and foot, pain often shows up in the buttock and down the leg [1]. A herniated disk may follow lifting, pulling, bending or twisting [1].
Smoking has been found to accelerate disk degeneration [1]. Disk degeneration is described as the leading cause of chronic back pain, and researchers are studying cell injections into disks [3]. Authors of that review say further high-quality trials are warranted [3].
Good to know
Aging-related changes in the spine do not keep most people from leading productive and generally pain-free lives [1].
Facet joints and ligaments change with age and can narrow the spinal canal
As disks shrink and the spine settles, more pressure lands on the facet joints, and they can develop wear-and-tear arthritis [2]. The tunnels where nerves exit the spine also become smaller [2].
The body responds to a worn joint by forming bone spurs to stabilize it [2]. The ligaments around the joints also grow thicker [2]. Together, spurs and thick ligaments crowd the space for the nerves [2].
Aging can also make it hard for joints and ligaments to hold the spine in position [1]. A vertebra can then slide forward on top of another, and if it slips too far the bones may press on spinal nerves [1].
Spinal stenosis squeezes the nerves inside a narrowed spinal canal
Spinal stenosis means the space around the spinal cord and spinal nerves has gotten smaller [2]. By age 50, up to 95% of people have some wear and tear in their spine, but stenosis happens most often in adults over 60 [2]. Arthritis is its most common cause [2]. Some people are born with a smaller canal, and wear can affect them sooner [2].
- An ache or burning pain that typically starts in the buttocks and moves down the leg, sometimes reaching the foot [2].
- Numbness or tingling in the buttocks or legs [2].
- Weakness in one or both legs, or foot drop, where the foot slaps on the ground while walking [2].
- Relief when you lean forward or sit, and more pain when you stand up straight or walk [2].
- Back pain that may or may not be present, depending on how much arthritis has developed [2].
Studies of the lumbar spine show that leaning forward can increase the space available for the nerves [2]. Some people note that they can ride a stationary bike or walk while leaning on a shopping cart [2].
Strained muscles and weak bones explain other common causes of back pain
Muscle soreness from activity is one of the more common causes of low back pain [1]. Muscle and ligament fibers can be overstretched or injured, often by an activity your body is not used to, such as the first softball game of the season or too much snow shoveling in one day [1]. This stiffness usually goes away within a few days [1].
Pain that does not go away within a few days may mean a disk injury [1].
Bones also weaken with age, a condition called osteoporosis [1]. In people with it, minor trauma such as sitting down forcefully on a hard chair or a ground-level fall can break a bone in the spine [1]. This is called a compression fracture, and it is a common cause of back pain in older adults [1].
Back pain with fever, chills or unexpected weight loss is a reason to call your doctor [1]. Talk to your primary care doctor if pain is always present no matter your activity or position, or if you have vascular or arterial disease or a history of cancer [1]. The same applies if back pain does not get better within a few weeks [1].
When to get care
Severe nerve compression in the lower spine needs emergency care
Severe squeezing of the nerves in the lower spine is rare, but it is considered a medical emergency that requires prompt treatment [2]. These signs need emergency care [2]:
- Numbness in your private area [2].
- Loss of control of your bowel or bladder [2].
- Losing strength in your legs or being unable to walk [2].
People with these severe nerve symptoms may need emergency surgery [2].
If you think you may have a medical emergency in the United States, call 911 or go to the nearest emergency room.
Imaging tests show different parts of the lumbar spine
Your doctor usually starts by looking at and pressing on your back and asking you to bend in different directions [2]. Your doctor may also check reflexes, strength and sensation in your legs to measure nerve function [1]. Other tests may help your doctor confirm a diagnosis [2].
| Test | What it shows |
|---|---|
| X-ray | Bones only, such as loss of disk height or bone spurs [2] |
| MRI | Soft tissues such as muscles, disks, nerves and the spinal cord [2] |
| CT scan | Cross-section images that show bony structures better than X-rays [2] |
| CT myelogram | Dye injected into the spine to show whether nerves are compressed [2] |
The shape of the lumbar spine changes when you move from lying down to standing, so scan position can affect an MRI result [4]. A review found that upright positioning is better for evaluating a vertebra slipping out of place [4].
Sources
- Low Back Pain orthoinfo.org
- Lumbar Spinal Stenosis orthoinfo.org
- Cellular transplantation and platelet-rich plasma injections for discogenic pain: a contemporary review Regenerative medicine
- Please be upstanding - A narrative review of evidence comparing upright to supine lumbar spine MRI Radiography (London, England : 1995)
Not medical advice. This page is general education written from the sources above. It cannot diagnose a condition or replace a licensed clinician who knows your history. If you may be having an emergency, call your local emergency number or go to the nearest emergency department.