Is it safe to excercise with a ligament tear?

It depends: What ligament is involved, severity of the tear (small partial tear, high-grade tear or full tear), risks of further injury- these are all questions that should be asked and answered. Finally, now does exercise affect the involved ligament? For example, one can often ride a bike with a grade i medial collateral ligament tear of the knee as way to maintain cardio and rehab the knee.