I have had an acl reconstruction done in nov 2011. is it ok for me to do yoga? is it necessary to avoid bending knee beyond 90 degrees?

Shoul have full ROM: You should have full motion and relatively few restrictions at this point. Best to talk to your surgeon about what specific restrictions you should follow-often depends on associated pathology (meniscus, articular cartilage, other ligaments), graft type (auto vs allograft), and progression through prior phases of rehab. Also ask about using a derotational brace for activity. Good luck!

Acl: It is okay for you to do yoga and bend your knee beyond 90 degrees.