Can joint hypermobility be dangerous?

Probably not.: Isolated joint hypermobility is not dangerous. When part of a syndrome like marfan's syndrome, there may be associated problems that are more serious. Marfan syndrome has a range of expressions, from mild to severe. The most serious complications are defects of the heart valves and aorta. It may also affect the lungs, the eyes, the dural sac surrounding the spinal cord, and the skeleton.

Not common form: Theory that uterus-lining tissue migrates to layer of tissue (peritoneum) lining the pelvic cavity & shedding blood at each menses.  alternative theory is hormone "relaxin" loosens pelvic ligaments already loosened by joint hypermobility syndrome, multiple childbirths or injury; causing tendonitis of transversus abdominis muscle at anterior superior iliac crests.  see my board quora.Com.