The Symphysis Pubis is supposed to spread. But only up to 9mm on average. Generally SPD is a combination of reaching the higher separation and a little misalignment, but is not spread further than 10mm. It often also includes the Sacroilliac Joint.

Diastasis of the Symphysis Pubis is a separation over 10mm. It is diagnosed by Ultrasound, Xray or MRI. It is more likely to render the sufferer immobile, and often includes a hospital stay and intensive physiotherapy.