Knee Popping (Crepitus): Causes, Red Flags, and When to See a Doctor

Knee crepitus is common and usually benign. Causes include:

1. Gas bubbles in synovial fluid bursting (cavitation).
2. Ligament/tendon snapping over bony prominences.
3. Loose bodies (cartilage fragments) catching.
4. Meniscus tear—often with pain, catching, swelling.
5. Osteoarthritis—bone-on-bone grinding, stiffness.
6. Quadriceps tendinopathy—pain at patellar tendon.

When to Seek Evaluation

• Persistent pain or swelling
• Locking, giving way, or restricted motion
• Sudden onset after injury
• Fever or systemic symptoms

Imaging (X-ray, MRI) may be needed to identify structural pathology.