context: When an arm or other extremity is amputated or lost, a prosthetic device, or prosthesis, can play an important role in rehabilitation. For many people, an artificial limb can improve mobility and the ability to manage daily activities, as well as provide the means to stay independent. There is a wide variety of prostheses that are designed to function -- and in many cases look -- like a natural arm, leg, hand, or foot. Although there are many different designs, most have similar parts. These include: A socket into which the stump of the amputated limb fits The suspension, which holds the prosthesis onto the stump The shaft The foot, hand, or hook A covering for cosmetic appearances The socket is often lined with foam or silicone to protect the stump. Special socks are also worn over the stump to ensure a proper fit and improve comfort. Following are some of the most common types of prostheses: Lower leg and foot. A number of prosthetic feet are available to simulate the action of a natural foot after an amputation below the knee. At least one available foot-ankle prosthesis is controlled by a microprocessor. It uses feedback from sensors to adjust joint movement, making walking more efficient and reducing the risk of falls. Leg with knee. For amputations above the knee, the prosthesis has both a knee and ankle joint. Currently there are more than 100 prosthetic ankle, foot, and knee models. Some use fluid or hydraulic-controlled devices that let users vary their walking speed. Others use computerized parts that let the user make rapid real-time adjustments while walking. Arm and hand. The oldest and most commonly used prosthetic arm is operated with the body's own movements and a harness that extends in a figure eight across the back and under the opposite arm. Others use a rechargeable battery to run small motors in the prosthetic hand or hook. The battery improves grip strength. A number of factors are involved in choosing a prosthesis. They include: The location and level of the amputation The condition of the remaining limb Your activity level, particularly for a prosthetic leg or foot Your specific goals and needs Prostheses are designed and fitted by a specialist called a prosthetist. The fitting process may begin in the hospital shortly after amputation after the swelling has gone and down and the incision is healed. It involves: Measuring the stump and the healthy opposite limb Making a plaster mold Fashioning the socket Attaching the shaft Aligning the prosthesis Depending on your comfort and how well your wound is healing, you may begin to practice with your artificial limb as early as a few weeks after surgery. A physical or occupational therapist will train you on how to use and care for it. To gain the greatest benefits of the new limb and help prevent problems, it is important to take care of the device, the amputation site, and your general health by doing the following every day: Remove the prosthesis before going to bed. Examine the device for loose parts or damage. Examine the stump for blisters or other signs of irritation. Clean and put a small amount of lotion on the stump and massage the skin. Place a bandage on the stump to decrease swelling when you are not wearing the prosthesis. Regularly inspect the skin of the stump to look for sores or wounds. You may need to have someone else help you look or use a mirror. Practice exercises recommended by your physical therapist. These will include exercises for stretching, range of motion, body positioning, and endurance. For leg prostheses, wear proper fitting shoes and never change the height of your heels. The prosthesis is designed for one heel height only. Clean the prosthesis' socket with soap and water. Wear clean dry socks with the prosthesis. It is also important to maintain a stable body weight. This will help to keep the prosthesis fitting properly. You should also have the prosthesis examined and serviced once a year to make sure it is in proper working order.