After my first child was born, I started having sacroiliac joint pain. My physical therapist says this can happen after childbirth. The pelvis separates and widens during childbirth. My doctor says it's not possible to have enough movement to cause pain. Who's right?

The SI joint has been a topic of interest in medicine for over 100 years. Hippocrates described pelvic separation during labor. He said it remained so after birth. Other doctors in the early 1900s reported pain coming from the SI joint after childbirth.

The SI joint is a true joint. It contains cartilage and synovial tissue. It's subject to the same age-related degenerative changes as any other synovial joint.

Large studies by well-known spine specialists report that SI dysfunction can be the main source of SI and low back pain. This can happen in women who aren't pregnant.

A recent study from Johns Hopkins University Medical School reported five percent of their SI patients had postpartum instability causing their symptoms. The evidence weighs in favor of your physical therapist's comments.