March 14, 2026
Author: Dr. Alexandru Grecu — Senior Orthopedic and Trauma Surgeon
Medically reviewed by Dr. Alexandru Florian Grecu, Senior Orthopedic Surgeon · Published: March 14, 2026 · Updated: 2 mai 2026
This is probably one of the most common questions: "Doctor, my knees crack—is it serious?" The short answer: most of the time, no. Painless crepitus is extremely common and benign.
Gas cavitation—the most common mechanism. The synovial fluid contains dissolved gases that form bubbles with certain movements. It's the equivalent of 'cracking' your knuckles—harmless.
Tendons gliding over bony prominences—a 'clicking' sensation common in young people and athletes.
Synovial plicae—folds of membrane that can get caught during movement, producing a 'click'.
Crepitus becomes relevant when it is associated with:
Pain—may indicate cartilage wear, a meniscus tear, or a loose body.
Swelling—the body is reacting to a pathological stimulus.
Locking—may suggest a loose fragment or a meniscus tear.
Instability—may indicate a ligament injury.
Continuous grinding (crepitus)—a sign of patellofemoral osteoarthritis.
In young people, painful crepitus in the anterior knee area often suggests chondromalacia patellae—premature wear of the kneecap cartilage. It manifests as pain when using stairs, sitting for long periods with knees bent, or squatting. It responds well to physical therapy.
Go if: the crepitus is painful, the knee swells, you feel locking or instability, it started suddenly after an injury, or you have continuous grinding.
No doctor is needed if: your knees crack occasionally without pain, without swelling, and you function normally.