When walking, climbing a flight of stairs, or running, you may hear occasional pops, snaps, crackles, creaking, or grinding when you bend or straighten your knee. These sounds are called crepitus (KREP-ih-dus).
One explanation for why this happens is osteoarthritis, but there are many other causes. Noisy knees by themselves are usually not a problem, however, if you have pain, too, you might want to consider asking your doctor to check out your knees.
Some causes of noisy knees are:
· Snapping of ligaments and tendons: Your knee joint is a hinge and it is stabilized by various ligaments to prevent the knee from moving beyond its limits. The ligaments and tendons often will move over bony prominences and can snap back similar to a rubber band.
· Popping bubbles: similar to cracking your knuckles, synovial or joint fluid can have small air bubbles that can pop during joint movement.
· Knee caps: The knee cap glides over the bony grooves between the top part and bottom part of the knee. Your knees may flex more than another person’s, for example, or your kneecaps may move more freely and this may cause some noise.
· Meniscus tears: The meniscus acts like a gasket inside the knee joint. Tears can occur from trauma or from repeated use during sports and running. Torn pieces of the meniscus can flip in and out of the joint cavity.
· Knee cap injury (chondromalacia patella): This is another cause of pain and noise from overuse injury. You may notice a dull ache behind the kneecap in addition to the crepitus.
· Runner’s knee (Patellofemoral syndrome): starts when you put too much force on the knee cap (patella). It happens before damage occurs in the joint surface of the patella, and it can lead to chondromalacia patella. This can involve a painful crunching and grating that you can see or hear when you move your knee.
· Knee osteoarthritis: loss of cartilage that cushions the joint over time. This causes inflammation and pain, and the joint may crackle and crunch. This is the common bone on bone sound.