Why do a person's knees click when bending them?

Knees noises are usually made because the surfaces of the knee glide across each other. It could also be due to the tightening of the ligaments when one is trying to bend the knee.

The clicking or popping sound around the knee is not a cause of concern since its a common occurrence. A person does not require medical attention unless the clicking is associated with pain and swelling. The clicking sound mostly occurs to people when they squat, as stated by WebMD. However, if the sound comes with pain and swelling, a person may need to visit a doctor. This could be a symptom of meniscus tears or cartilage injury.