Describe the grating, crackling or popping sounds and sensations experienced under the skin and joints.

• A. Edema
• B. Erythema
• C. Dyspnea
• D. Crepitus

Answer: (D)

Crepitus is the crackling, grating, or popping sensation or sound you feel or hear under the skin or in a joint. In joints, it happens when roughened cartilage or other joint surfaces rub together, or when gas bubbles in the synovial fluid pop as the joint moves. When air is trapped in the soft tissues after injury or infection, subcutaneous crepitus produces a palpable crackling sensation under the skin. This is different from edema, which is swelling from fluid buildup and feels tense or puffy, and from erythema, which is skin redness due to inflammation. It’s also not related to shortness of breath, which is dyspnea. Recognizing crepitus helps distinguish mechanical or soft-tissue air findings from purely inflammatory signs.