I'm a nurse in a pediatric hospital unit. We had a child come in over the weekend with septic sacroiliitis. I learned in school that this was a problem for drug addicts. Is it possible that's how this child got this condition?

Septic (infectious) sacroiliitis can occur in young children as a result of a staph infection that has traveled via the blood to the sacroiliac joint and infected it. The condition is rare accounting for only 1.5 per cent of all pediatric cases of septic arthritis.

The diagnosis can be difficult to make. The physician uses clinical symptoms, lab findings, and imaging studies to determine the cause of the symptoms. And the symptoms can vary from back pain to knee pain to buttock pain with or without a limp when walking. There may be a fever, chills, or other similar symptoms.

Other equally rare disorders that can mimic septic arthritis include bone tumor or blood disease. Joint aspiration is one way to test and diagnose septic sacroiliitis. But it can be a painful and unpleasant procedure for the child. MRI may be a much better choice. The detail on the MRI is enough to tell the difference between sacroiliitis and a muscle abscess.

Intravenous drug use/abuse is one cause of septic sacroiliitis in the adult population. Other risk factors for adults include trauma and pregnancy. The most common cause in both age groups is infections of other systems such as an ear or bladder infection.