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04 May 2022

Back pain: anatomy, causes, & scans you might need

symptoms 5 minutes reading time

If you’re curious about upper, middle, or lower back pain causes, you aren’t alone. Back pain is an extremely common complaint in doctor’s offices everywhere, but many people struggle to understand why their back pain happens. Read on to learn more about the back’s anatomy, causes of back pain, and treatments.

Your back’s anatomy: the spine & what surrounds it

The back is made of muscles, ligaments, nerves, joints, and stacked individual bones (vertebrae) that support your body’s foundation: the spinal column.1 People are born with 33 individual vertebrae, but, by adulthood, most spines are down to 24 individual bones, plus the sacrum (a fusion of several smaller bones) and coccyx (tailbone).

Your spine is roughly divided into four areas:

  1. The cervical (upper) spine covers the 7 bones in your neck;
  2. The thoracic (middle) spine is comprised of the 12 chest and mid-back bones;
  3. The lumbar (lower) spine is 5 bones (or 6, in some cases–an additional vertebral bone, or transitional body, is not uncommon) in your lower back; and
  4. The sacral spine, or sacrum, is the bottommost part of your back, and is made of several fused vertebral bodies. This sits above the tailbone.

The spinal column is an incredibly important piece of anatomy because it supports about half of the body’s overall weight and guards the spinal cord. It also protects large nerves that extend to the arms and legs and the small nerves between vertebrae. Vertebrae are connected by flexible joints called facets, and are cushioned by shock absorbers called discs.

The structures that support the spinal column are both strong and sensitive. Disease, irritation, and injury to any of its structures can cause back pain, varying in severity from mildly annoying to totally incapacitating.

Back pain causes

Muscle injuries. When certain parts of the spine are strained or sprained, the surrounding soft tissues inflame, which can lead to muscle pain, stiffness, and even spasm (a painful, rigid type of cramping).2 This inflammation occurs as a protective mechanism in response to a trauma or injury, awkward movement (bending, sitting, or sleeping), lifting something too heavy, general overuse, poor posture, and even emotional distress. This kind of muscle pain is often felt in the lower back. Regular exercise, stretching, and staying hydrated can help you prevent back pain in some cases, but it can’t always be avoided.

Bulging or ruptured discs. Sometimes, the soft material inside your intervertebral discs–those shock absorbers between bones–can slip, bulge, or rupture (herniate), compressing a nerve and causing pain on the affected side of the body.3 Herniated discs are to blame for a significant number of upper and lower back pain cases. Spinal stenosis, a narrowing of spinal cord space, can also cause nerve root compression. These conditions can cause localized or radiating pain, numbness, tingling, or weakness in your arms or legs. Lower back pain that shoots down your buttocks and/or legs is called sciatica. If the herniated disc is in your neck, the pain may radiate sharply down your shoulder and arm. Pain in the extremities may be worsened by sudden movements or certain positions.

Arthritis. Arthritis is when the cartilage that covers a bone’s joint thins out. It can be a normal part of the aging process and is often, but not always, painful.4 When the protective cushioning that cartilage normally provides is weakened or dissolved, bone can grind on bone, causing painful stiffening of the joints and restricting certain ranges of movement.  Cartilage can break down naturally due to wear and tear (osteoarthritis), inflammatory diseases (rheumatoid arthritis), or predispositions to genetic conditions (degenerative disc disease). Osteoarthritis and rheumatoid arthritis are the most common types of arthritis.

Tumors. Primary spinal tumors–ones that originate in the spine–are fairly uncommon, accounting for only 10% of all spinal tumors each year; most spinal tumors are metastatic, and have spread to the spine from somewhere else in the body.5 When spinal tumors grow, they can weaken the spinal cord and its nerves, leading to pain, weakness, and physical instability. Pain is a common and often first sign of a spinal tumor, particularly if it is worse upon waking or during the night. (Tumors cause inflammation. Your adrenal system, which is responsible for creating your body’s natural anti-inflammatory agents, is not making steroids while you sleep.) If a tumor is especially close to a major nerve, you may experience neurological symptoms like tingling (paresthesia), weakness, balance issues, or even incontinence.

Infections. Spinal canal infections are caused by bacteria or fungi and account for a much smaller overall percentage of back pain cases. The most common causes of these infections are the bacteria staph and E. coli. Certain surgical procedures, intravenous drug use, and even flexion (bending) injuries can introduce these infectious bodies to the spinal canal. Infections in major organs can also cause back pain in different parts of the back (kidney infection typically causes middle back pain; liver infection typically causes upper-right back pain; appendicitis usually causes lower-right back pain).

The road to diagnosis, treatment, & managing pain

Back pain is a very general term, which can make its causes tricky to diagnose and treat. Since many instances of back pain are caused by relatively harmless factors like age, strain, or stress, the road from symptom onset to diagnosis is an exhausting odyssey of trial, error, and watch-and-wait.

Sometimes, the first line of treatment is pain management. Back pain can be relieved by using heat or cold compresses, massage, rest, gentle stretching, topical anesthetics, anti-inflammatory drugs, or prescription muscle relaxers.

If these ameliorative measures aren’t giving you relief, or if your back pain is chronic, your doctor may dig deeper and ask questions that can help them rule out a more serious or urgent diagnosis. It will be helpful for you to be able to describe your pain and how it affects your ability to function on a given day.

If your doctor has reason to suspect there is a specific condition, disease, or injury causing your pain, they may order one or several tests:

  • X-rays can show issues with bone breaks and alignment issues.
  • CT scans and MRIs can show specific problems in your nerves, discs, blood vessels, ligaments, and muscles.
  • Bone scans can detect bone tumors and osteoporosis-caused compression fractures.
  • Blood tests and nerve studies can identify or rule out other causes of back pain.

Scheduling your scan

Uncovering the reason for your upper, middle, or lower back pain might involve a bit of investigating and testing, but we’re here to help you get to the root of it. Head over to scan.com’s easy-to-use scan search tool to find a diagnostic imaging center near you.


  1. cedars-sinai.org: Anatomy of the Spine | Cedars-Sinai

  2. aans.org: AANS Patient Resources - Neurosurgical Conditions and Treatments

  3. mayoclinic.org: Diseases and Conditions - Mayo Clinic

  4. hopkinsmedicine.org: Conditions and Diseases | Johns Hopkins Medicine

  5. mskcc.org: Spine Tumors & Spinal Cancer | Memorial Sloan Kettering Cancer Center

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