The project

(First, please check our video posted in October 2023 on "Cluneal nerve entrapment" and the "back mice phenomenon")

I am Marta Cañis Parera. I am a medical doctor from nearby Barcelona. On February 2018, I started my Ph.D. studies about “fatty tissue and low back pain” in the Universitat Rovira i Virgili from Reus, Spain.

As part of my Ph.D. studies I am doing a bibliographic review about fatty tissue as a cause of low back pain. Within my thesis project I am under the construction of this web page called, where I plan to share this bibliographic review (in 4 main chapters) and write a blog with my personal views  at the same time.

The aim of the project is to share the information about this entity that still seems to be under-recognized by many doctors nowadays, and to make it a useful tool for me to share information with other researchers or people who may have a special interest in it.

*We have published a review about back mice: you may access a free on line pdf in the following link → Historical Review of Studies on Sacroiliac Fatty Nodules (Recently Termed “Back Mice”) as a Potential Cause of Low Back Pain. Cañis Parera et al. Pain ther (2021).

-LINK to a Youtube video based on a presentation I did in December 2022 in Poland. It summarizes well what we know so far about the ‘back mice’ phenomenon.

26 Replies to “The project”

  1. This website has been a Godsend! Thank you for all of your research and for posting it online for the benefit of everyone. I just had a back mouse removed today! I have many photos of the procedure if you’d like me to share those with you. My surgeon even admitted after researching this herself, she believes she has one too that has been misdiagnosed! It’s amazing that such a small piece of fat can wreak such havoc and that so many people are suffering due to this mostly unknown problem. Thanks again for all that you have done and are doing. You’ve definitely made a difference in my life. Keep up the great work!

    1. Hi Erica, so wonderful to hear you found a surgeon who could be helpful! Could you please share their name? That would be so amazing, if you wouldn’t mind. Thank you so much.

  2. Hi Marta

    Thanks for the information on your site. It’s part of what helped me get answers for my cluneal nerve entrapment that I had suffered with for 3 years.

    I had surgery last week and I am feeling so much better after the removal of two episacral lipomas… one of them over 5x3x3cm

    I do have a quick question for you. In your literature review, have you come across any information on recovery time? I think I’ve had about an 80% reduction in pain. Have you read anything about the time it takes for the pain to resolve following surgery? Ie should I anticipate further resolution with healing and with the swelling going down etc.

    I am seeing my specialist next week for follow up I am just interested to hear about the literature.

    1. Hi Rachel,
      Thanks for writing.
      According to the articles some patients have immediate relief and some others take a while. Specially if there is a formation of a seroma or hematoma at the surgical side. Did they place any drainage to you? But I can’t tell you a specific recovery post-op time.

  3. Thanks so much Marta

    I certainly don’t have the qualifications to say what it is but there is certainly some type of swelling at the incision site. I think the fact that others have said it can take time makes me feel less worried. I just hope I continue to see improvement. It’s definately been significant to date.

    I am not sure of the medical terms but I have two lipomas one in each of the ‘dimples of venus’. The incision was above each lipoma.

    I did not have drains inserted.

    Thanks again Marta.


  4. Hi thank you for this article. I fell in 2012 and been passes from one person to the next. Do I mention this to the pain clinic where I’ve had shots before, or my physician? Again, thank you. I have so many they almost run together from lower back down to sciatic and into hip where there is a large bursitis. We are moving and I’m bent over and everything gets hard and more pronounced as does the pain. Many thanks. Jina

    1. Hi Jina,
      Thanks for you message. I hope the web site can help you. Please always check with your doctors.


  5. For nearly a decade now I’ve been telling doctors and specialists that these knots on my lower back/hips/butt are excruciatingly painful, I have referred pain that basically from my waist down. And time and time again it’s been disregarded and I’ve been misdiagnosed. I finally feel vilified and I’m not crazy. Now to just find a dr that will listen and remove them so I can have a life again. They’re huge and debilitating. Thank you so much for this!! I finally feel like I have answers!!

    1. Hi Leona,
      I am a doctor myself and I was never thought about backmice during my career and during the past years. Last year after my husband had one I decided to search about the nodules. I think that we doctors many times still forget that there are still many fields in medicine to be studied, and sometimes we tend to dismiss patients opinion, unfortunately. I am trying to study and discover the scientific reasons why such a entity, backmice (that are mainly localized painful edema of the deep fatty tissue that cause peripheral neuropathy) can be so painful, patients can also help on that work by explaining to doctors that “want to listen” about it. In medicine we have neglected both things: the fatty tissue and the peripheral nerves as a main causative pain agents. If you need help tell me.

    2. Leona – I have had 5 removed. I see a plastic surgeon. Try there. See one that is affiliated with an orthopedic practice and not one that is 100% cosmetic.

  6. Hello, I have been suffering from severe lower back pain in these areas for over 10 years. I had looked into what the lumps were several years ago and couldn’t find much information other than. Dr 1937 who discovered them. My question is would I need an orthopedic surgeon or general surgeon. I actually see my pcp tomorrow and will have her feel them . I do find when I’m confined to my chair at work for long periods without moving about seems to exacerbate pain to where it stiffens and doing any task such as sweeping, mopping . Bending over seems to really cause intense burning and throbbing. I will keep you posted. I’m so glad to have found other people that have had removal and 100 percent relief . My Fnp I see should be able to shoot me up with lidocaine to see if that provides any relief .
    Thank you so much for sharing your information and starting a place where to find help.

    1. Hello Tara,
      Thanks for writing.
      In Spain, as far as I know, nobody gets operated from backmice, but I would think it will be a GENERAL SURGEON matter. Maybe many patients get diagnosed just as a “lumbar painful lipoma” and some may be operated. According to the published articles many got relieved.

      The question is that nowadays most of the “LOW BACK PAIN” in medicine is categorized as “UNSPECIFIC LOW BACK PAIN”. Unspecific because MEDICINE DOES NOT HAVE YET AN EXPLANATION. SOMEHOW it seems that we paid little attention to the FATTY TISSUE as a causative agent (despite the great work of some authors like COPEMAN).

      Apparently the fatty tissue that provoques backmice tends to EDEMATIZE EASYLY and if the edema get confined or encapsulated it causes compression with local pain and even peripheral neuropathy (CLUNEAL NERVE NEUROPATHY in the lower back). Many causes have been described to cause this edematization and subsequent increase of pain: cold dampness, stress, hormones, too much resting or sitting, fever…

      Tell me If I can help you further,

  7. Any remedies that can reduce the pain associated with back mice other than an injection or removal? Does ice or heat provide any relief or a combination of the two? Many thanks in advance, Nick

    1. Hello Nick,

      According to the studies: HEAT, compression and certain specific massage techniques -that I do not know- may also be helpful (although some patients refer they get worst after certain manipulative techniques or just after the nodules are pressed, so massage is a tricky option).
      If it is possible soft physical exercise is also recommended.

      Marta Cañis Parera

  8. I am very glad that I found this website. Thank you for doing such an amazing job.
    It’s been years that I have been dealing with pain in my iliac crest, but I have lumps in that area. I had lipomas removed 2 years ago one on each side of my lower iliac crest, but the problem is that it came back again on mi right side and we got it removed, and I had relief for months but again it came back on the same side and same spot. Do you know why this would happened? I am having a hard time finding a surgeon now because I have had them removed twice already.
    Some times I feel like I just want to grab a knife and remove them myself and maybe someone will take me seriously 🙁
    I am going to email my pcp right now and tell him
    About this website.
    I can’t keep taking the controlled medications that I take, there is no need if they could be removed
    Thank you again and wish me luck
    I just would like to know why they keep coming back

    1. Hello Rocia Beuke,

      I am Marta Cañis. Indeed many medical articles reported that back mice tend to come back (recurrence) in SOME patients after a period of months/years. As far as I know none of the medical articles could found an explanation for that. Did you try to manage pain with local anesthetic injections as a first step before surgery?


  9. Hi! It,s Jose M Climent, PR&M MD from Alicante. Thank you so much, your work is encouraging and your web is friendly and nice. I’ve been working for a long time in MSK pain, including back pain, and injecting back mice from 20 years ago. Some patients are very grateful following these treatments. I’m especially enjoying   the great recovery  of historic papers. I think ultrasound is too a good help to locate, study (size, position) and inject accurately and safely back mices. Thank you, you are great!

    Bon dia, soc Josep María Climent, metge de rehabilitació d’Alacant. Moltíssimes gràcies per un treball tan estimulant i per una web tan xula y atractiva. Treballe des de fa més de 20 anys en dolor musculoesquelétic, per suposat també en mal d’esquena.  Sempre he considerat el lipomes sacroliacs com una diana terapéutica si el malalt els reconeix com el seu dolor a la palpació. Els trate amb infiltració i alguns malalts queden molt agraïts amb el tractament. Agraïsc especialment la collita de articles històrics, sembla una tasca exhaustiva i que ens ajuda i ensenya profundament.Pense que la ecografía es de gran ayuda en el diagnostic i en la mesura i posicionament dels fibrolipomes. Igualmente millora la precisió i la seguretat de les infiltración. Jo la faig servir habitualment  amb molta satisfacció. Moltes gràcies, ha estat meravellós trobar esta web, continuaré visitant-la i la recomanaré. Ben fet!

    1. Hola Jose!
      Moltes gàcires pel missatge.
      Com vas ser coneixedor dels lipomes sacroiliacs?… ja que són bastant desconeguts per la majoría de metges en general.
      Marta Cañis Parera

      1. Hola, gràcies per contestar! Vaig començar amb la palpació i el interrogant de que podría ser ja que no trovaba literatura. Amb pacéncia finalment troví el concepte de “back mouse” i ja vaig situar-me millor. Després ho he lligat al atrapament dels nervis cluneals, sempre que trove semiología neuropática, y/o a la disfunció sacroiliaca. Quan el palpe, i hi ha signe de reconeiximent del dolor per el malalt, propose la infiltració, a vegades ayuda, no siempre, el mal d’esquema es molt complexe.
        Igualmente ho comente en les arrases i recomane la búsqueda i el tractament. La eco ajuda a reconeixerlo, mesurar-lo i punjarlo amb precisió, tinc algunes imatges. A horas d’ara, solc infiltrar-los conjuntament amb la sacroiliaca, si els trobe. Pense que son un factor mes, una diana terapéutica relevant en la lumbalgia.
        Com a anécdota, en els meus inicis profesionals, vaig trobar un ratolí d’esquena ben gros (fa 30 anys) molt sintomático i molt definir a la palpació. Vaig convencer a una cirujana plástica per traure-lo i demanar una biopsia. JO pensaba que sería un lipoma, pero la cirujana ho va definir com “greix” . La AP va dir teixit greixós. Curiosament, la malalta ve millorar completament.
        La resposta a la teua pregunta, com vaig ser coneixedor, va ser per curiositat intel.lectual médica.

        1. Gràcies per l’explicació. Un dels nostres propers projectes també implica l’ús de la punció eco-guiada.

          Però jo estic més centrada en aprofundir en el coneixement de l’anatomia del teixit greixòs i les fascies per entrendre aquestes formacions nodulars descrites com a herniacions per alguns cirurgians. Que en el cas dels back mice sempre sembla donar-se en la mateixa ubicació i moltes vegades de forma bilateral. Crec que sabem massa poc de l’anatomia i la fisiologia del teixit greixòs i la seva fascia, i per això no entenem la fisiopatologia dels ratolins de l’esquena.

          Moltes gràcies de nou.

  10. Hi! My name is Sharon. I cried and cried the other day. I went to a spine and pain specialist. I was once again told that my pain was pretty much in my head. I was told I have arthritis and some degenerative disc’s. All normal age-related disorders. I had multiple x-rays, an MRI and 3 rounds of physical therapy. I keep telling the Drs it is not my arthritis or disc’s or muscles that hurt. I point directly to the fatty nodules and I’m told that they cannot possibly be the cause of my pain. I have spent about 5 years in pain. I’m 54 years old now and very healthy and active but sometimes I am debilitated by this. I need help finding help. Is there anyone I can turn to? I live near Portland Oregon. My next plan is to just see a naturopathic Dr since my physician doesn’t know what to do with me. I’m at a loss here and yet, I know what I have are back mice. How is it, in this day and age, that no one is willing to accept this as a diagnosis??

    1. Hi Sharon,

      Maybe you should tell your doctors to check for “superior cluneal entrapment”. That entity it is easier that they know.

      Best wishes,

  11. I read that lipoma are composed of triglycerides. What if we all suffer from too many triglycerides? I’m testing that by taking fenofibrate

  12. Hi Marta,

    Thanks for this site . It has been very helpful. I have 2 lipomas both on my sacroiliac crest . I had one removed but I am still in so much pain it seems it may have grown back and or I have nerve damage or the nerve is still being compressed . I have had 2 pretty Normal lumbar spine and pelvic mri. I had one normal ‘emg and one abnormal . I am in Boston and have been in pain for over a year . Touching and massage the area around the lipoma and pressing on the bone kills. Is there anything you recommend . Thanks for your time .


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