Knee clicking or popping, especially when fully extended, is common. While sometimes alarming, these sounds are often not a concern. Understanding their source helps determine when medical attention is needed.
Common Reasons for Knee Clicking
A frequent, harmless cause of knee clicking is the release of gas bubbles within the joint’s synovial fluid. This fluid, which lubricates the joint, contains dissolved gases. When the knee moves and the joint space expands, pressure drops, causing bubbles to form and rapidly collapse, producing a pop or click. This phenomenon, known as cavitation, is similar to cracking knuckles and does not indicate joint damage.
Another benign reason involves the movement of tendons or ligaments. As the knee extends, these tissues can temporarily catch on a bony prominence or shift before snapping back into place. This often creates a click or thud. These clicks are typically painless and do not suggest an underlying problem.
When Clicking Indicates an Underlying Issue
While many knee clicks are benign, some signal an underlying problem, especially when accompanied by other symptoms. A common cause for problematic clicking is a meniscus tear. The menisci are C-shaped cartilage pieces that cushion the knee joint. If this cartilage tears, it can get caught within the joint during movement, leading to clicking, popping, or catching.
Patellofemoral pain syndrome, or “runner’s knee,” can also cause clicking or grinding. This condition involves issues with how the kneecap (patella) tracks in its groove. Misalignment or roughness on the kneecap can lead to friction and noise during knee extension.
Less commonly, loose bodies within the joint cause clicking. These are small fragments of bone or cartilage that float freely within the synovial fluid. When these fragments get trapped between joint surfaces, they can cause a click, catch, or even locking.
Signs That Warrant Medical Consultation
Seek medical attention if knee clicking is accompanied by “red flag” symptoms. Persistent pain is a primary indicator that the clicking is more than a harmless noise. Swelling around the knee, especially if sudden or prolonged, also warrants evaluation.
Other concerning signs include warmth, instability (where the knee feels like it “gives way”), or inability to bear weight. If clicking started after an injury (like a fall or twist), or if the knee feels locked and cannot be straightened or bent fully, professional assessment is important. These symptoms suggest a potential injury to ligaments, cartilage, or other knee structures.
Approaches to Knee Health and Management
Maintaining knee health supports joint function and can reduce benign clicking. A healthy weight is beneficial, as excess body weight stresses the knee joints. Regular low-impact exercises (like swimming, cycling, or walking) strengthen knee muscles without excessive strain.
Exercises targeting quadriceps and hamstrings enhance knee stability and support. Stretching these muscles also improves flexibility and range of motion. Using proper form during physical activities and avoiding aggravating movements protects the joint. For non-painful clicks, simple self-care measures like rest and avoiding provoking activities are often sufficient.