What are Back Mice? Understanding Painful Lumps in the Back

Individuals may discover a lump, bump, or nodule under the skin around their lower back, hips, and sacrum that can cause pain by compressing nerves and damaging the fascia. Can knowing the conditions linked to them and their symptoms help healthcare providers determine a correct diagnosis and develop an effective treatment plan for them?

Painful Bumps, Nodules Around Low Back, Hips, and Sacrum

Painful masses in and around the hips, the sacrum, and the lower back are lumps of fat or lipomas, fibrous tissue, or other types of nodules that move when pressed on. Some healthcare providers and chiropractors, in particular, use the non-medical term back mice (In 1937, the term was used to describe lumps associated with episacroiliac lipoma) to describe the bumps. Some healthcare professionals argue against calling the masses mice because it is not specific and could lead to misdiagnoses or incorrect treatment.

• Most show up in the lower back and hip area.
• In some cases, they protrude or herniate through the lumbodorsal fascia or the network of connective tissue that covers the deep muscles of the lower and middle back.
• Other lumps can develop in the tissue under the skin.

Today, many conditions are associated with back mice lumps, including:

• Iliac crest pain syndrome
• Multifidus triangle syndrome
• Lumbar fascial fat herniation
• Lumbosacral (sacrum) fat herniation
• Episacral lipoma

Related Conditions

Iliac Crest Pain Syndrome

• Also known as iliolumbar syndrome, iliac crest pain syndrome develops when a tear in the ligament occurs.
• The ligament band connects the fourth and fifth lumbar vertebrae with the ilium on the same side. (Dąbrowski, K. Ciszek, B. 2023)
• Causes include:
• Tearing the ligament from repeated bending and twisting.
• Trauma or fracture of the ilium bone caused by a fall or vehicle collision accident.

Multifidus Triangle Syndrome

• Multifidus triangle syndrome develops when the multifidus muscles along the spine weaken and diminish function or ability.
• These muscles can atrophy, and intramuscular fatty tissue can replace the muscle.
• Atrophied muscles decrease the spine’s stability and can cause lower back pain. (Seyedhoseinpoor, T. et al., 2022)

Lumbar Facial Fat Herniation

• The lumbodorsal fascia is a thin fibrous membrane covering the back’s deep muscles.
• Lumbar fascial fat herniation is a painful mass of fat that protrudes or herniates through the membrane, gets trapped and inflamed, and causes pain.
• The causes of this type of herniation are currently unknown.

Lumbosacral (Sacrum) Fat Herniation

• Lumbosacral describes where the lumbar spine meets the sacrum.
• Lumbosacral fat herniation is a painful mass like lumbar facial herniation in a different location around the sacrum.
• The causes of this type of herniation are currently unknown.

Episacral Lipoma

Episacral lipoma is a small painful nodule under the skin that primarily develops over the top outer edges of the pelvic bone. These lumps occur when a portion of the dorsal fat pad protrudes through a tear in the thoracodorsal fascia, the connective tissue that helps hold the back muscles in place. (Erdem, H. R. et al., 2013) A healthcare provider may refer an individual to an orthopedist or orthopedic surgeon for this lipoma. An individual may also find pain relief from a massage therapist familiar with the condition. (Erdem, H. R. et al., 2013)

Symptoms

Back lumps can often be seen under the skin. They are typically tender to the touch and can make sitting in a chair or lying on the back difficult, as they often appear on the hip bones and sacroiliac region. (Bicket, M. C. et al., 2016) The nodules may:

• Be firm or tight.
• Have an elastic feel.
• Move under the skin when pressed.
• Cause intense, severe pain.
• The pain results from pressure on the lump, which compresses the nerves.
• Damage to the underlying fascia can also cause pain symptoms.

Diagnosis

Some individuals do not realize they have nodules or lumps until pressure is applied. Chiropractors and massage therapists often find them during treatments but do not diagnose the abnormal fatty growth. The chiropractor or massage therapist will refer the patient to a qualified dermatologist or medical professional who can perform imaging studies and a biopsy. Determining what the lumps are can be challenging because they are non-specific. Healthcare providers sometimes diagnose the nodules by injecting them with a local anesthetic. (Bicket, M. C. et al., 2016)

Differential Diagnosis

The fatty deposits can be any number of things, and the same applies to the sources of nerve pain. A healthcare provider may further diagnose by ruling out other causes, which can include:

Sebaceous Cysts

• A benign, fluid-filled capsule between the layers of skin.

Subcutaneous Abscess

• A collection of pus beneath the skin.
• Usually painful.
• It can become inflamed.

Sciatica

• Radiating nerve pain down one or both legs that is caused by a herniated disc, bone spur, or spasming muscles in the lower back.

Liposarcoma

• Malignant tumors can sometimes appear as fatty growths in the muscles.
• Liposarcoma is typically diagnosed by biopsy, where some tissue is removed from the nodule and examined for cancer cells. (Johns Hopkins Medicine. 2024)
• An MRI or CT scan may also be performed to determine the exact location of the nodule.
• Painful lipomas are also associated with fibromyalgia.

Treatment

Back nodules are usually benign, so there’s no reason to remove them unless they’re causing pain or mobility problems (American Academy of Orthopedic Surgeons: OrthoInfo. 2023). However, they should be examined to make sure they are not cancerous. Treatment usually involves injected anesthetics, such as lidocaine or corticosteroids, as well as over-the-counter pain relievers like NSAIDs.

Surgery

If pain is severe, surgical removal may be recommended. This involves cutting out the mass and repairing the fascia for lasting relief. However, removal may not be recommended if there are many nodules, as some individuals can have hundreds. Liposuction may be effective if the lumps are smaller, more extensive, and comprise more fluid. (American Family Physician. 2002) Complications of surgical removal can include:

• Scarring
• Bruising
• Uneven skin texture
• Infection

Complementary and Alternative Treatment

Complimentary and Alternative Medicine treatments like acupuncture, dry needling, and spinal manipulation can help. Many chiropractors believe back nodules can be successfully treated with complementary and alternative therapies. A common approach uses acupuncture and spinal manipulation in combination. A case study reported that anesthetic injections followed by dry needling, which is similar to acupuncture, improved pain relief. (Bicket, M. C. et al., 2016)

Injury Medical Chiropractic and Functional Medicine Clinic specializes in progressive therapies and functional rehabilitation procedures focused on restoring normal body functions after trauma and soft tissue injuries and the complete recovery process. Our areas of practice include Wellness & Nutrition, Chronic Pain, Personal Injury, Auto Accident Care, Work Injuries, Back Injury, Low Back Pain, Neck Pain, Migraine Headaches, Sports Injuries, Severe Sciatica, Scoliosis, Complex Herniated Discs, Fibromyalgia, Chronic Pain, Complex Injuries, Stress Management, Functional Medicine Treatments, and in-scope care protocols. If the individual requires other treatment, they will be referred to a clinic or physician best suited for their condition, as Dr. Jimenez has teamed with the top surgeons, clinical specialists, medical researchers, therapists, trainers, and premiere rehabilitation providers.

Beyond the Surface

References

Dąbrowski, K., & Ciszek, B. (2023). Anatomy and morphology of iliolumbar ligament. Surgical and radiologic anatomy : SRA, 45(2), 169–173. doi.org/10.1007/s00276-022-03070-y

Seyedhoseinpoor, T., Taghipour, M., Dadgoo, M., Sanjari, M. A., Takamjani, I. E., Kazemnejad, A., Khoshamooz, Y., & Hides, J. (2022). Alteration of lumbar muscle morphology and composition in relation to low back pain: a systematic review and meta-analysis. The spine journal : official journal of the North American Spine Society, 22(4), 660–676. doi.org/10.1016/j.spinee.2021.10.018

Erdem, H. R., Nacır, B., Özeri, Z., & Karagöz, A. (2013). Episakral lipoma: Bel ağrısının tedavi edilebilir bir nedeni [Episacral lipoma: a treatable cause of low back pain]. Agri : Agri (Algoloji) Dernegi’nin Yayin organidir = The journal of the Turkish Society of Algology, 25(2), 83–86. doi.org/10.5505/agri.2013.63626

Bicket, M. C., Simmons, C., & Zheng, Y. (2016). The Best-Laid Plans of “Back Mice” and Men: A Case Report and Literature Review of Episacroiliac Lipoma. Pain physician, 19(3), 181–188.

Johns Hopkins Medicine. (2024). Liposarcoma. www.hopkinsmedicine.org/health/conditions-and-diseases/sarcoma/liposarcoma

American Academy of Orthopedic Surgeons: OrthoInfo. (2023). Lipoma. orthoinfo.aaos.org/en/diseases–conditions/lipoma

American Family Physician. (2002). Lipoma excision. American Family Physician, 65(5), 901-905. www.aafp.org/pubs/afp/issues/2002/0301/p901.html