When one cracks a knuckle, the stretching of the capsule lowers the pressure inside the joint and creates a vacuum which is filled by the gas previously dissolved in the synovial fluid. This creates a âbubbleâ which then bursts producing the characteristic âpoppingâ or âcrackingâ sound.
DOCTORS: Click here for the Professional Version. Burns are injuries to tissue that result from heat, electricity, radiation, or chemicals. Burns cause varying degrees of pain, blisters, swelling, and skin loss. Deep, extensive burns can cause serious complications, such as shock and severe infections. Small, shallow burns may need only to be kept clean and to have an antibiotic cream applied.
Sunburn (also called erythema) is caused by overexposure to ultraviolet radiation (UV rays). While the symptoms are usually temporary (like red skin that is painful to the touch), skin damage is cumulative throughout a person's life and can develop into serious long-term health effects, including skin cancer. Mild sunburn results in skin irritation and redness and can be safely treated at home.