Knee Crepitus: When Noises Are Normal vs. Pathologic

Knee sounds (crepitus, clicking, popping) are extremely common and usually benign.

Benign (Physiologic) Causes

• Gas bubble collapse (cavitation): Synovial fluid pressure changes → "pop".
• Tendon/ligament snapping: Iliotibial band, patellar tendon over bony prominences.
• Patellofemoral maltracking (asymptomatic): Minor facet engagement.
• Age‑related cartilage thinning: Rougher surfaces → grinding sensation (crepitus) without pain.

Potentially Pathologic Features

• Painful crepitus (especially weight‑bearing).
• Swelling, effusion.
• Mechanical symptoms: locking, giving way.
• History of trauma.
• Progressive worsening.

Common Pathologic Causes

• Meniscal tear (mechanical click/pop).
• Chondromalacia patella / osteoarthritis.
• Loose body (osteochondral fragment).
• Plica syndrome (medial plica snap).
• Patellofemoral instability.

Evaluation

• History + exam (McMurray, Thessaly, patellar grind).
• Weight‑bearing X‑rays (AP, lateral, Merchant).
• MRI if mechanical symptoms or surgical candidate.

Management

• Asymptomatic: Reassurance, activity modification, quad/hip strengthening.
• Symptomatic: PT (hip/core/quad), NSAIDs, bracing, injections (corticosteroid, HA, PRP), surgery if mechanical block.