I am 60/male. i felt a pain on the left side of my right leg near my knee. it made it difficult to walk. it went away but returned & went away. cause?

Pop in knee: There are a variety of explanations but this is most likely related to cartilage or tendons. Although a physical examination may determine the cause, an MRI will likely establish the diagnosis. Splinting with supervised therapy may be an option or surgery (arthroscopic or open) may be indicated.

Knee pain: I will need more information such as whether rest made it go away, whether excercise made it worse, recent or remote history of trauma, relationship of pain to climbing steps or descent, associated locking, how close the pain is to the back of the knee. If you can provide more information, it will be easier to help you.