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Clicking, cracking, or popping sounds issuing from the knee are actually very common – most people will experience sounds from their knees at some point in their lifetime. Your knees may click when bending or straightening the knee or walking up and downstairs.
The name given to crackling knees is crepitus. In general, crepitus is not a cause for concern. However, if your clicking knees are accompanied by pain or a reduced range of motion in the knee, you may need to seek treatment.
What causes crepitus?
There are a number of potential causes of crepitus.
Gas bubbles
Gas can build over time in the synovial fluid surrounding the joint. Bending your knee can cause the bubbles to burst, leading to a popping sound. This happens to most people at some stage of their life and is not a cause for concern. The popping sound should not be accompanied by pain. It’s the same effect as cracking your knuckles.
Patellofemoral joint
The kneecap slides in the patellofemoral joint and can sometimes make a grating sound due to the uneven surface. Knees vary from person to person – for example, some knee joints are more worn by age or use, or some people’s kneecaps may move more freely. This can cause some individuals to have knees that are more prone to making noise than others.
Ligaments/tendons
These tight bands of tissue may flick over each other or over bony parts of the knee, resulting in a clicking sensation. You may hear the clicking noise as they snap back into place after bending your knee.
Knee injury
Injury to your knee can cause crepitus. Injury can be caused by overuse, such as ‘runner’s knee,’ or by an accident or fall. Most knee injuries that result in crepitus will also be accompanied by pain or aching in or around the knee joint.
Arthritis
Osteoarthritis is most common in people over the age of 50 and is usually the result of wear and tear. Osteoarthritis in the knee sees a breakdown of cartilage around the knee joint, leading to pain, inflammation, and crunching or crackling sounds issuing from the knee.
Knee replacement surgery
Following surgery such as a knee replacement, you might be more keenly aware of sensations and noises issuing from your knee. You may experience crepitus after a knee replacement, but if it’s not combined with pain, it’s likely harmless.