I had a chronically dislocating shoulder that was operated on two years ago. Since then I've been symptom-free and no problems. Is it safe to assume it won't dislocate again if it hasn't by now?

That's a fair assessment. Most recurrence of shoulder instability occurs in the first six months in shoulders that have multidirectional instability. That means the joint capsule has been damaged or stretched out in the front and in the back. If nothing's happened by the end of two years the joint is probably healed, strong, and stable.

Of course, a traumatic injury or accident could cause another dislocation. Any joint that's subjected to loads greater than it can handle can dislocate. Your risk for recurrence of the problem increases if you play contact sports like rugby, football, or soccer. A bad fall or car accident are two other common ways to reinjure a repaired shoulder.