Popping, or crepitus (grinding, creaking, cracking, grating, or crunching) in the knee is a common symptom in people of all ages. Most of the time it is not a serious problem. Painless popping is due to the lining tissue of the knee (synovium) being compressed when the knee moves. This is a normal occurrence in many knees. This popping can be more noticeable with certain movements of the knee, and can sometimes not be noticeable for long peroiods of time.
Painful popping is much less common. That is most commonly found in degenerative (“wear-and-tear”) arthritis. This popping can also be intermittant or as the joint gets more inflamed, can occur on a regular basis. Painful popping in the knee can less commonly be caused by patella abnormalities, cartilage problems, or loose fragments in the knee. Painful popping should be evaluated by an orthopedic surgeon.