Facet Joint Pain (Facetogenic Back Pain)

What it is

Each level of your spine is joined to the next in three places: the disc at the front, and a pair of small joints at the back, one on the left and one on the right. These are the facet joints. Each one is about the size of a thumbnail and is built like any other joint in the body, with smooth cartilage on both surfaces, a capsule around it, and a little fluid inside. The facet joints guide the way each level moves and stop it from sliding or twisting too far.

Like the joints in your knees and fingers, facet joints can wear. The cartilage thins, the bone underneath thickens and grows spurs, and the capsule becomes inflamed and tender. When a worn or irritated facet joint is the main source of someone's back pain, it is called facet joint pain, or facetogenic back pain.

Facet joints and discs wear together. As a disc loses height, the facet joints behind it carry more load than they were designed for, so the two problems often go hand in hand, and sometimes it takes some care to work out which one is driving the pain. Facet pain accounts for somewhere between one in six and one in three cases of long-lasting low back pain, depending on the study, and it becomes more common with age.

What it feels like

• An ache off to the side. Facet pain usually sits an inch or two to one side of the midline, in the muscles beside the spine, and people can often press a thumb right onto the sore joint. It can be on one side or both.
• Standing and arching back hurt. Standing in one place, reaching overhead, leaning backward, and walking downhill all close the facet joints and press the worn surfaces together. Standing at a counter or in a line is a common complaint.
• Twisting hurts. Turning to look behind you, swinging a golf club, or reaching across your body loads the joints on one side.
• Morning stiffness. The back is stiff and sore getting out of bed and loosens up over the first twenty or thirty minutes of moving. Rolling over in bed can wake you.
• Sitting and bending forward usually help. Sitting down, leaning forward over a shopping cart, or lying curled on your side opens the joints and eases the ache. This is the reverse of discogenic pain, which is worse with sitting and bending.
• Pain that spreads to the buttock and thigh. An irritated facet joint commonly refers pain into the buttock, the side of the hip, and the back of the thigh. It usually stays above the knee and does not cause true numbness or weakness in the foot.
• Flares after an awkward move. A twist while lifting, a long day on your feet, or a bad night's sleep can set off a flare that lasts days to a couple of weeks, then settles.

Why an irritated facet joint can cause leg pain without a pinched nerve

The nerve root that leaves the spine at each level passes right in front of the facet joint, through an opening called the foramen. When a facet joint is inflamed, the capsule swells, fluid can leak out of it, and the tissues around the opening become irritated. The nerve root next door is bathed in that inflammation, and it can respond with pain, tingling, or a burning feeling down the leg that mimics sciatica, even though nothing is pinching it.

Like the leg pain that comes from an irritated disc, these symptoms are usually temporary. They come on with a flare of the joint and fade over days to a few weeks as the inflammation settles, often with nothing more than time, movement, and a short course of anti-inflammatory medicine. They tend to be vaguer and milder than true sciatica, and they do not come with weakness.

Two things can turn this into a lasting problem rather than a passing one, and I look for both. A bone spur on a worn facet joint can narrow the opening and press on the nerve for good; that is foraminal stenosis. And an inflamed joint sometimes blows out a small fluid-filled pouch, called a synovial cyst, which can sit against the nerve. When leg pain is severe, follows one strip of skin, comes with numbness or weakness, or lasts more than six weeks, I treat it as a true lumbar radiculopathy and look for its cause.

How we diagnose it

Your story points the way: pain to one side, worse with standing, arching, and twisting, better with sitting and bending forward, and stiff in the morning. On exam I press over the joints and have you lean back and twist toward the sore side, which usually reproduces the pain, and I check that your nerves are working normally.

X-rays and MRI show worn facet joints, but I read them with caution, because worn facet joints appear on the scans of most people over fifty, including people with no back pain at all. The imaging confirms that the joints are worn; it cannot tell me that they are the source of your pain.

The test that can is a medial branch block. Each facet joint sends its pain signal through a tiny nerve called the medial branch, which crosses a bony landmark on the side of the vertebra. Under X-ray guidance, a small amount of numbing medicine is placed on that nerve. If your usual pain drops by at least half, and ideally more, while the medicine is working, the joints are the source. If it does not change, we look elsewhere. I do not treat a facet joint as the culprit until it has passed this test.

How we treat it

Most people improve without surgery. The order I usually follow:

• Keep moving, and change positions often. Standing still is the hardest thing for a facet joint. If your work keeps you on your feet, rest one foot on a low step or rail and switch feet, and take a sitting break every half hour or so.
• A flexion-biased program. Exercises that gently round the low back and strengthen the deep abdominal and hip muscles open the facet joints and take load off them. I have written out a starting program in my flexion-based home program for low back pain. Bring it to your therapist.
• Core strength and posture for the long run. A stronger trunk and less sway in the low back mean less pressure on the joints with every step. My core program for low back pain is the maintenance plan, and a healthy weight helps more than most people expect.
• Heat in the morning. A warm shower or heating pad before you start moving shortens the stiff period.
• Medicines. An anti-inflammatory for a limited time, with food, if your stomach and kidneys allow it. Acetaminophen for day-to-day control.
• A steroid injection into the joint. For a stubborn flare, an injection of anti-inflammatory medicine into the facet joint under X-ray can settle it for weeks to months and let you do the therapy properly.
• Treating the nerve to the joint. If a medial branch block has shown that the joints are the source, the next step is to quiet the nerve that carries their pain signal. The usual method is radiofrequency ablation, which heats the nerve through a needle; relief lasts six to twelve months on average and the treatment is repeated when it wears off. For people whose relief keeps wearing off, I offer an endoscopic medial branch transection, which cuts and removes a segment of the nerve under direct vision so that it cannot reconnect as easily.

Surgery on the joint itself is almost never the answer for facet pain alone. Fusion is reserved for only when it is truly needed, usually when a worn level has become unstable or has slipped, and a painful facet joint on its own is not that reason: a fused level stops moving and shifts extra load onto the facet joints above and below it, which can speed their wear.

The science: for the curious

Each level of the spine works as a three-joint complex: the disc and the two facet joints behind it. Load that one of them stops carrying goes to the other two, which is why facet arthritis tends to follow disc wear by a few years and why I rarely see one without the other in people past middle age.

Each facet joint receives its pain fibers from two medial branches, one from the nerve at its own level and one from the level above. That is why a proper medial branch block numbs two small nerves for each joint being tested, and why an ablation or transection treats two nerves per joint. The medial branch carries only sensation from the joint and the supply to a small muscle beside the spine, so interrupting it does not weaken the legs or change their feeling.

The pain that facet joints refer into the buttock and thigh follows patterns that were mapped out decades ago by injecting the joints of volunteers: the lower lumbar joints refer pain to the buttock and the back of the thigh, the upper ones to the flank and the front of the thigh. The brain cannot tell a signal from a deep joint apart from a signal from the skin and muscle that share the same nerves, so it reports the pain where it expects it. That overlap is why facet pain mimics sciatica and hip disease, and why the numbing test, not the scan, settles the question.

When to call

Call if the pain is spreading below the knee and not settling, if you notice new numbness or weakness in the leg or foot, if the leg symptoms are still present after six weeks of a proper program, if you have a fever with back pain, or if morning stiffness lasts more than an hour and you are under forty, which can point to an inflammatory arthritis rather than wear. New trouble controlling your bladder or bowels, or numbness in the groin and inner thighs, is an emergency: go to the nearest emergency room or call 911.

Learn more

OrthoInfo, Low Back Pain: orthoinfo.aaos.org (opens in a new tab)

OrthoInfo, Spinal Injections: orthoinfo.aaos.org (opens in a new tab)

My guides to discogenic back pain and annular tears, the other common source of mechanical back pain, to lumbar radiculopathy, and to lumbar foraminal stenosis; my flexion-based home program for low back pain; and my page on endoscopic medial branch transection.

This handout is general education about a common condition and does not replace the personalized advice we discuss in clinic. If anything here does not match what we talked about, what we talked about wins: please ask me.