Crohn's disease sometimes causes muscle achiness or weakness. There is no single or straightforward explanation for what causes weak muscles, which can make it frustrating to diagnose and treat.

The most likely causes of muscle weakness in Crohn's patients seem to fall into two main categories: nutritional deficiencies and co-existing diseases.

Nutritional deficiencies

Crohn's disease causes inflammation in your digestive tract, disrupting your body's ability to absorb important nutrients from the food you eat. As a result, patients may become deficient in one or more vitamins and minerals that support critical functions in your body.

Crohn's patients often become deficient in vitamin D and potassium, both of which may indirectly cause muscle weakness. Vitamin D has many important jobs. It helps us absorb calcium, which our body uses to build and maintain strong bones. Thirty to 60 percent of people with Crohn's are vitamin D deficient. This puts them at risk for osteomalacia, a disease that results from a defect in the bone-building process. Osteomalacia causes soft bones and one of its symptoms is achy muscles. Osteomalcia is particularly common in patients who have had surgery to remove their small intestine. Corticosteroid drugs, often prescribed to treat Crohn's disease, may also cause vitamin D deficiency.

Potassium is essential for the proper response of nerves to stimulation and in muscle contractions. When Crohn's patients lose too much potassium through severe vomiting or diarrhea, for example, they may develop hypokalemia. Like osteomalacia, hypokealemia also causes muscle weakness.

A healthy, balanced diet that includes adequate protein and vitamin and mineral supplements can minimize deficiency-related muscle problems.

Other diseases

Other diseases that co-exist with Crohn's may also cause muscle problems. Fibromyalgia, for example, is a painful condition of the bones, muscles and joints. There is a high incidence of Fibromyalgia in Crohn's patients.

Rhabdomyolysis and myositis are less common diseases that both cause muscle problems. Rhabdomyolysis often results from direct trauma and causes injury or death to skeletal muscles, producing myalgia, or muscle pain. Although it's not common, hypokalemia due to potassium deficiency may cause Rhabdomyolysis. Patients with both Rhabdomyolysis and Crohn's disease may frequently be misdiagnosed.

Myositis refers to the swelling of muscles. It is relatively rare and is more likely to occur in people who already have immune system disorders, such as Crohn's disease. Physicians who treat Crohn's patients with unexplained muscle weaknesses should evaluate them for myositis.

Don't assume muscle weakness is inevitable because you have Crohn's disease. If you suspect there is something else going on, discuss it with your physician.


Dig Liver Dis. 2008 Feb;40(2):149-50.