Crohn’s disease can cause back pain, a connection that often surprises people because the condition is primarily known for affecting the digestive tract. As a chronic inflammatory disorder, the inflammation can extend beyond the gut, leading to several distinct mechanisms of back pain. These include systemic joint inflammation, localized intestinal complications, and long-term effects on bone structure.
Systemic Joint Inflammation
The most common cause of back pain in people with Crohn’s disease is inflammatory arthritis, an extraintestinal manifestation frequently involving the joints. Up to 25% of individuals with inflammatory bowel disease experience chronic lower back pain. A specific type of inflammatory disorder, axial spondyloarthritis (AxSpA), causes inflammation in the spine and the sacroiliac joints, which connect the lower spine to the pelvis. This inflammation is called sacroiliitis and is a significant source of deep pain in the lower back and hips.
Inflammatory back pain is distinct from common mechanical back pain. It typically develops slowly over time and is often worse after periods of rest, such as in the early morning. The stiffness and pain associated with AxSpA usually improve significantly with movement or exercise, a pattern that helps distinguish it from mechanical pain, which tends to worsen with activity.
Referred Pain from Intestinal Complications
Localized inflammation or infection within the abdomen can cause pain signals to be mistakenly interpreted by the brain as originating in the back, a phenomenon known as referred pain. Crohn’s disease complications often involve the retroperitoneal space, the area behind the abdominal lining.
Inflammation or pus-filled pockets, called abscesses, can form near the intestinal wall and irritate or directly involve the psoas muscle, a large muscle that runs along the lower spine. A psoas abscess, which occurs in about 10% of Crohn’s patients with intra-abdominal abscesses, causes progressive, acute pain in the lower back or hip. This pain may be accompanied by systemic signs of infection, such as fever. The pain may be partially relieved by lying down with the knee bent and raised, a posture that relaxes the irritated psoas muscle.
Bone Health and Structural Changes
Long-term Crohn’s disease and its treatment can weaken the skeletal structure, leading to back pain from mechanical causes. This is primarily due to malabsorption and the side effects of certain medications. Chronic inflammation interferes with the absorption of essential nutrients, particularly Vitamin D and Calcium, necessary for maintaining bone density.
The use of corticosteroids, a common treatment for Crohn’s flares, is a significant risk factor for bone loss because these drugs disrupt the natural cycle of bone breakdown and rebuilding. This leads to a reduction in bone mineral density, known as osteopenia, which can progress to osteoporosis. Weakened vertebrae can suffer microfractures or compression fractures, causing chronic back pain, height loss, and changes in posture.
Diagnostic Steps and Treatment Options
Addressing back pain in a patient with Crohn’s disease begins with accurately identifying the underlying cause: systemic inflammation, localized infection, or structural bone weakness. A physician, often working with a rheumatologist or gastroenterologist, uses different diagnostic tools depending on the suspected origin of the pain.
Diagnostic Tools
Blood tests check for inflammatory markers like C-reactive protein (CRP) or Erythrocyte Sedimentation Rate (ESR), which point toward active inflammation. Imaging is used to pinpoint the location and nature of the problem: X-rays can show damage to the sacroiliac joints, an MRI can detect early inflammatory changes in the spine, and a CT scan is often used to locate abdominal or psoas abscesses. Bone mineral density is measured using a dual-energy X-ray absorptiometry (DXA) scan to diagnose osteopenia or osteoporosis.
Treatment Approaches
Treatment is tailored to the diagnosis. For systemic joint inflammation like AxSpA, therapy often involves biologic medications, such as TNF-alpha inhibitors, which treat both the gut and joint inflammation simultaneously. If an abscess or infection is the cause, treatment involves antibiotics and potentially surgical or percutaneous drainage. For pain related to bone health, management focuses on calcium and Vitamin D supplementation, and sometimes medications like bisphosphonates; physical therapy is also recommended to improve mobility and strengthen core muscles.