Understanding Back Mice, aka Episacroiliac Lipoma

Back of the pelvis including sacroiliac area.
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Back mouse is a condition characterized by painful bumps in and around the hips, sacrum and low back. Accurately diagnosing it is often a stumper for doctors and other health practitioners. Because of this, carefully considering the treatment recommendations you are offered — should you find yourself with these painful nodules — is absolutely key to getting better.

Let's sort out the known facts and give you a reference for dealing with this painful problem effectively.


Back mice have been known to surgeons since 1937 when Reis reportedly named them episacroiliac lipoma. Since then, a number of names have been attributed to this condition including: Iliac crest pain syndrome, multifidus triangle syndrome, lumbar fascial fat herniation and lumbosacral fat herniation.

Many authors believe that of all the terms used to identify back mouse, the last two — lumbar fascial fat herniation and lumbosacral fat herniation — provide the most accurate descriptions for this condition.

So what is back mice? Basically, it's the appearance of little fat masses that protrude abnormally through the lumbodorsal fascia.The lumbodorsal fascia is a big diamond-shaped sheath of connective tissue located in the low and mid-back areas.

The fat masses tend to have a firm, rubbery quality to them. You might also find them on the hip bones in back, as well as the sacroiliac region.

Back Mice Symptoms

Now, you might think that a simple fat mass couldn't cause much pain, but in this case, at least, you would be incorrect. Patients — and their surgeons — often report excruciating pain from back mice.

Along with the pain, telltale symptoms may include visibly notable nodules in the low back and sacral areas that when touched or pressed reproduce the type of pain that likely drove you to seek treatment in the first place.

Very few research studies have been conducted on the topic of back mice, and that may explain why so little is know about it in the spine care profession. Articles written online by chiropractor David W. Bond may provide the most comprehensive information on this subject. 

Bond reports that moderately obese women seem to be at a higher risk for back mice than others. He also says that people with back mice quite often go through a battery of treatments with no pain relief to show for it.

Diagnosis and Treatment

One way to diagnose back mice is by injection. Surgery is another way. 

If injecting a local anesthetic relieves the pain — albeit temporarily — the diagnosis is suggested. Case studies from the 1940s show that when back mice are surgically removed, this almost always fully relieves the pain.

Currently, surgery consists of excision of the mice, followed by repair of the fascial openings through which they emerged. This procedure appears to be the only way to achieve durable pain relief from back mice.

The problem is, you might have hundreds of back mice, which will likely make it difficult for your surgeon to eliminate each and every one.

That said, Bond, who is a chiropractor, believes this condition may be successfully treated by combining acupuncture and spinal manipulation.

A 2016 medical case study and review of literature found that injecting a local anesthetic or steroids into the nodules, followed by dry needling may lead to pain relief. The same study found just one clinical trial comparing an injection of local anesthetic to a saline  solution. In this study, the injections were not followed by dry needling, and patients reported only mild and fleeting pain relief.

Let's Not Get Confused — Conditions whose Symptoms are Similar to Back Mice


As mentioned above, it's not uncommon for doctors to misdiagnose back mice. And sciatica is the most common misdiagnosis they settle on.

Why? What's the correlation between back mouse and pain and other symptoms that go down one leg?

While pain from back mice starts locally, at the nodules themselves, like sciatica, it often radiates to other areas. Also like sciatica, back mouse pain tends to be unilateral, and may increase depending on your position. The pattern of pain radiation is generally not uniform.

Bond says that irritation that comes from back mouse doesn't show up on nerve root tests — unless you also have a herniated disc. He adds that the condition may be accompanied by spasms in your paraspinal muscles, as well as decreased lumbar range of motion. Pain intensity can vary, as may duration.

Trigger Points

While it's possible to pinpoint back mouse pain and/or tenderness by touching one of the critters, back mice are not trigger points. Trigger points present themselves as taut bands muscle while back mice are felt as masses or nodules.

Back mice are not tight muscles either, so pressing down on them will not contribute to their cure or management, as many massage therapists may believe. In fact, this kind of treatment, which may work great for trigger points, causes pain, Bond says. This means that a deep massage will likely not be the correct treatment.

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