Left lower back pain

A patient initially complained of left low back pain; however, there were no specific findings in plain radiography of the lumbar spine and pelvis. In addition, blood chemistry test findings were normal. Magnetic resonance imaging (MRI) revealed a diffuse bone marrow oedema in the left SIJ. Conservative treatment was effective, and the pain was relieved within 3 months. However, 2 months later, a similar pain developed on the right side.