Final answer:
The discomfort and pain during recovery from hand or foot surgery or injury are caused by edema due to the accumulation of fluids, which is exacerbated when the limb is not elevated.
Step-by-step explanation:
During recovery from surgery or injury to hands or feet, it is crucial to elevate the limb to prevent discomfort and pain. The discomfort is primarily caused by edema, which is the accumulation of excess water in the tissues. When the body part is not elevated, gravity can contribute to an increased accumulation of fluid in the limb's soft tissues. This condition can lead to the swelling of subcutaneous tissues and result in stretched, tight skin that causes pain. Moreover, the increased fluid in the tissues can press against nerves, adding to the discomfort.
Blood flow relies significantly on the skeletal muscle pump, particularly in the lower limbs. When a limb is injured or post-surgery, the muscles might not be used as much, weakening this 'pumping' action and leading to blood pooling and additional fluid leakage into the surrounding tissues. Elevating the limb above the heart level helps to reduce gravitational pressure and assists the returning flow of blood and lymphatic fluid back towards the central circulation, thereby minimizing edema and the consequent pain and discomfort.