What causes clicking or popping sounds during knee flexion and extension?

A clicking or popping sound during knee flexion and extension may result from prolonged inactivity followed by sudden, intense physical activity, which can create negative pressure within the joint cavity. Alternatively, it may be caused by conditions such as calcium deficiency, knee osteophyte formation (bone spurs), or meniscal injury. If the patient experiences accompanying pain, they should consult a healthcare provider for evaluation to determine the underlying cause and receive appropriate treatment.