05 Oct The Gut–Joint Connection: What the Evidence Actually Supports
Many of our patients notice a pattern: when their stomach acts up, their joints feel worse. That’s not a coincidence.
Your gut holds more immune cells than anywhere else in your body. The lining of your intestines is where your immune system does much of its daily work, sorting out what’s a threat and what’s harmless. When that process gets thrown off, the effects can show up far from your stomach — including in your joints.
The Strongest Link: Ankylosing Spondylitis
The clearest connection is with ankylosing spondylitis, a type of inflammatory arthritis that affects the spine.
About 5 to 10% of people with this condition also have inflammatory bowel disease, meaning Crohn’s disease or ulcerative colitis. Here’s the surprising part: when doctors examine the intestines of people with ankylosing spondylitis, roughly half to two-thirds show signs of inflammation — even when they feel no stomach symptoms at all.
Researchers now think the gut and the joints aren’t causing each other’s problems. Both are being driven by the same underlying process.
That’s why our team asks about bowel habits when patients come in with inflammatory back pain. If you have ongoing diarrhea along with back pain, that’s worth looking into with a gastroenterologist.
Rheumatoid arthritis shows a gut link too. People with RA tend to have different gut bacteria than people without it, and gum disease is clearly tied to RA risk. These findings are real, but we can’t yet say the bacteria cause the arthritis. It may work the other way around.
Two Claims That Need Context
“Leaky gut.” Your intestinal lining can become more permeable, letting things pass through that normally wouldn’t. This is measurable, and it does show up in several rheumatic diseases. What we don’t know is whether it causes disease or happens because of inflammation already underway. Be cautious about anyone offering to “heal” your leaky gut as a treatment.
Fibromyalgia is not an autoimmune disease. You’ll often see it listed online alongside lupus and RA. Fibromyalgia affects how the body processes pain — it isn’t the immune system attacking tissue. Stomach symptoms are common with fibromyalgia and overlap heavily with IBS, but the reason is different.
Why Digestion Matters for Your Bones
This connection is well established. Celiac disease and Crohn’s disease make it harder to absorb calcium, vitamin D, and protein, and both are recognized causes of osteoporosis. Weight loss surgery and long-term acid reflux medication are also tied to lower bone density.
If you have osteoporosis with no clear explanation, getting tested for celiac disease makes sense. Not sure of your own risk? Our osteoporosis questionnaire is a good place to start.
One clarification: IBS doesn’t block nutrient absorption, so it isn’t a bone risk on its own — though it can make eating well harder. Menopause timing also plays a major role in bone health. Read more about menopause and bone health here.
Simple Steps That Help
- Add fiber slowly, from a variety of plants
- Eat fermented foods like yogurt, kefir, or sauerkraut
- Cut back on ultra-processed foods
- Protect your sleep
- Manage stress
These feed a healthier mix of gut bacteria. You don’t need an elimination diet — those often backfire.
When to Get Checked Out
See a doctor rather than trying a new diet if you have ongoing diarrhea, blood in your stool, weight loss you can’t explain, severe stomach pain, or nutrient deficiencies that keep returning.
At Island Rheumatology & Osteoporosis, we treat digestive symptoms as part of the whole picture, not a separate problem. When the gut turns out to be central to what’s going on, we coordinate with gastroenterology. Request an appointment to talk it through with our team.
