After sitting with right leg under my left i go to streighten it out and it feels like it's locked, painful then it pops in. what can i do?

Meniscus?: It is possible that you have a tear in your meniscus which is the cartilage cushion in the knee. This condition can often cause locking, popping and pain. First I would avoid the sitting position that triggers the problem until you see the orthopedic specialist for evaluation and treatment.

Remember the Tin Man: The older we get (and I'm with you!), we need to change position more frequently than we used to or we get stiff. Like the Tin Man in The Wizard of Oz, we should be able to tote an oil can around with us to lube our rusty, squeaky, painful joints. You may also have arthritis in that knee or other joint problems. See your doc and get evaluated. Till then limit sitting in that position for now.