Knee clicking is common, often leading to questions about its meaning. These sounds, medically termed crepitus, can range from soft clicks to louder pops and affect a significant portion of the population. While frequently a harmless byproduct of normal joint function, knee clicking can sometimes signal an underlying issue that warrants attention.
Normal Knee Noises
One common cause is joint cavitation, which involves the release of tiny gas bubbles, primarily nitrogen, accumulated within the synovial fluid that lubricates the knee joint. As the joint moves and pressure changes, these bubbles can collapse or burst, producing an audible clicking or popping sound, similar to cracking knuckles.
Another reason for normal knee sounds involves the movement of tendons or ligaments. These soft tissues can sometimes momentarily catch or snap over bony prominences or other structures within the knee joint as it bends or straightens. This motion creates a clicking or popping sound as the tissue glides back into place. These noises are generally painless and do not suggest structural damage.
When Knee Clicking Signals an Issue
If clicking is associated with pain, swelling, stiffness, or a feeling of locking or catching, it may indicate a meniscus tear. A torn meniscus, the C-shaped cartilage cushioning the knee, can result in loose pieces of cartilage catching within the joint, causing painful clicking and potentially limiting movement.
Cartilage damage, such as that seen in osteoarthritis, can also cause problematic knee noises. When the smooth cartilage surfaces in the joint wear down, bones may rub together, leading to grinding or popping sounds often accompanied by discomfort. Patellofemoral pain syndrome, sometimes called “runner’s knee,” occurs when there is excessive stress or misalignment between the kneecap and thigh bone, which can result in a crunching or grinding noise, particularly when straightening the knee. A loud pop experienced at the time of an injury, especially if followed by immediate swelling or instability, can indicate a more severe issue like a ligament tear, such as an anterior cruciate ligament (ACL) injury.
Managing Knee Clicking
When experiencing knee clicking, initial steps depend on whether other symptoms are present. If the clicking is painless and not accompanied by swelling or functional limitations, gentle movement and continued activity are recommended. Rest alone is not typically beneficial for painless clicking; instead, physical activity can help maintain knee health.
If knee clicking is accompanied by persistent pain, swelling, stiffness, a feeling of instability, or an inability to bear weight, seeking professional medical advice is advisable. A doctor will conduct a physical examination to assess knee movement and stability. Imaging tests, such as X-rays or an MRI, may be ordered to visualize the internal structures of the knee and identify any damage to cartilage, ligaments, or meniscus. Treatment for problematic clicking often includes physical therapy to strengthen muscles, anti-inflammatory medications to reduce pain and swelling, or other non-surgical interventions.