My left knee has a torn cartilage which is really painful. i can't fully bend my knee when i lie down. popping and locking as well. surgery or not?

Possibly: Has torn cartilage been confirmed by an MRI? How long have you had symptoms? Have other treatments been tried, and did they help? If you have a torn meniscus that is causing significant pain, swelling or locking, then knee arthroscopy, a "scope," can be helpful to remove or repair the torn meniscus. If I can help, then join my care team & virtual practice at www.healthtap.com/dr-clarkeholmes