Hello,
The pain behind the knee you describe mimics the symptoms of a Patella tendon problem.
I had the same problem with my left knee recently, which was not yoga related.
You should go and see an orthopedist. They can tell you whether its strained or torn. Sometimes X-rays do not show tears and an MRI is required to confirm micro tears which could lead to bigger problems if not taken care of properly.
I would advise a proper knee brace to be worn, rest and aleve for inflammation until properly healed. I waited close to 3 weeks before I went back to hot yoga.
I occasionally feel residual discomfort which gets less and less frequent. I believe hot yoga done with conscious limitation has helped me greatly.
Good luck!
