Why is my knee swollen and popping when i walk?

Something new?: Swelling from knee can be from trauma/injury, infection(i.E lyme disease), gout, and rheumatologic diseases etc.. Sometime effusion/swelling occurs without known cause. When it is swollen, the knee is less stable and popping and "giving-out" can occur. Take it easy, becareful walking on uneven ground/steps. Motrin/aleve may help. Consult doc to find the cause/treatment. Good luck.