How do i tell if my tendon is ruptured?

Tendon can't support: If a tendon is truly torn, ruptured, it can't function with full strength. If it is your leg, you will not be able to stand. An easy way to check is to compare to the good side.

You need evaluation: I need more details to answer. You need to be evaluated clinically, we may need to do some tests, like mris or us. In the hand lack of function could be a clue for a tendon injury.