Have you been using fluoroquinolone antibiotics frequently?
Cipro, Levaquin, Avelox?

These have been shown to affect tendon metabolism and integrity. When severe the tendons may rupture. This is not well understood yet, esp why some people are more affected than others.

There are also genetic tendencies as mentioned in the previous posts. It also might be an issue with people with Marfan's syndrome. This is a genetic problem with collagen maintenance.
People with Marfan's also have weak artery walls and need supervision to prevent dissections. They are taller than normal and sometimes have rib cage abnormalities too..but the Marfan's females I've known had very mild physical signs. It was their male children who had it severely. One had a tendon injury in a sprained ankle that did not heal up properly and she had to have a special operation by an orthopedic surgeon.

There are some supplements to target tendon issues, and they typically contain some form of plant product with silica and also magnesium. Some foods are higher in silica than others, whole grains (not processed), green beans, bananas.
http://www.vitalhealthzone.com/nutri...of-silica.html

You can search foods high in silica and see if you are eating those.