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.
All burns should be treated quickly to reduce the temperature of the burned area and reduce damage to the skin and underlying tissue (if the burn is severe). First-Degree Burns First-degree burns, the mildest of the three, are limited to the top layer of skin: 1  Signs and symptoms: These burns produce redness, pain, and minor swelling. The skin is dry without blisters. 2  Healing time: Healing time is about 3 to 6 days; the superficial skin layer over the burn may peel off in 1 or 2 days.