Suggest Treatment For Ligament Tear In Knee Joint

Hello, my knee pops everytime I bend it. I went and got a MRI done and the film shows no ligament tears. My knee feels very weak after I play basketball and I'm not able to lift 5lbs while doing leg extension. I also had reconstructive ACL surgery on the knee in 2000 and my knee stated to pop about 6 months ago. I don't know whats wrong. Need help?