These amputations result almost equally from an injury (as in a motor vehicle crash or during combat) or from a surgical procedure to treat a complication of a disorder (such as decreased circulation due to atherosclerosis or diabetes). The leg can be amputated below the knee, above the knee, or at the hip. Or a foot or one or more toes may be amputated.

After leg amputation, most people are fitted for an artificial leg (a lower-limb prosthesis). Components may include toes, a foot, and, for an above-the-knee amputation, a knee unit. Newer prostheses that are controlled by microprocessors and powered myoelectrically or prostheses with bionic components enable people to control movements with more precision.

Rehabilitation includes exercises for general conditioning and exercises to stretch the hip and knee and to strengthen all arm and leg muscles. The person is encouraged to begin standing and balancing exercises with parallel bars as soon as possible. Endurance exercises may be needed. The specific program prescribed depends on whether one or both legs were amputated and how much of the leg was amputated.

The muscles near the amputated limb or at the hip or knee joint tend to shorten. This shortening (called contractures) usually results from sitting in a chair or wheelchair for a long time or from lying in bed with the body out of alignment. Contractures limit the range of motion. If a contracture is severe, a prosthesis may not fit correctly, or the person may become unable to use the prosthesis. Therapists or nurses teach the person ways to prevent contractures.

Therapists help people learn how to condition the residual limb (stump), which promotes the natural process of shrinking. The residual limb must shrink before a prosthesis is fitted. An elastic shrinker or bandages worn 24 hours a day can help shape the residual limb and prevent fluid buildup in tissues. Soon after the amputation, people may be given a temporary prosthesis so that they may begin walking sooner and thus help the residual limb shrink. With a temporary prosthesis, people can start ambulation exercises on parallel bars and progress to walking with crutches or a cane until a permanent prosthesis is made. Sometimes people use a prosthesis with permanent components but with a temporary socket and frame. Because some parts remain the same, people may adjust to the new parts more quickly.

If a permanent prosthesis is made before the residual limb stops shrinking, adjustments may be needed to make it comfortable and to enable people to walk well. A permanent prosthesis is usually made several weeks after amputation to give the residual limb time to shrink completely.

When people receive the prosthesis, they are taught the basics of using it:

Training is usually continued, preferably by a team of specialists. A physical therapist develops a program of exercises to improve strength, balance, flexibility, and cardiovascular fitness. The therapist teaches people more about how to walk with a prosthesis. Walking begins with direct assistance and progresses to walking with a walker, then with a cane. Within a few weeks, many people walk without a cane. The therapist teaches them to use stairs, walk up and down hills, and cross other uneven surfaces. Younger people may be taught to run and participate in athletic activities. Progress is slower and more limited for people who have above-the-knee amputation, for older people, and for people who are weak or poorly motivated.

The prosthesis needed for an above-the-knee amputation weighs much more than that for a below-the-knee amputation, and controlling a prosthetic knee joint requires skill. Walking requires 10 to 40% more energy after a below-the-knee amputation and 60 to 100% more energy after an above-the-knee amputation.