Changes in muscles, bones and joints contribute to weakness in the legs of elderly people, explains MedlinePlus. These conditions also lead to changes in gait and posture and cause the person to move more slowly.
The changes in lean muscle tissue often begin in the 20s for men and 40s for women. The rate of the loss of lean muscle mass is a genetic-related condition. The body begins to deposit the pigment lipofuscin and fat in the muscles. The muscle fibers lose some elasticity, and the body becomes less efficient at replacing muscle due to aging, reports MedlinePlus.
While aging adults lose bone mass, the problem is often more evident in women after menopause, indicates MedlinePlus. These changes in bone tissue affect the spine, arches of the feet and long bones of the body. These changes in posture affect leg strength.
Joint problems are common to almost all older adults, according to MedlinePlus. Arthritis and other types of joint problems reduce the flexibility of the legs. Fluids build up around the joints and calcium deposits increase. As movement becomes more difficult for the older adult, he may limit his exercise, further contributing to muscle weakness. The aging process causes a lack of stability when walking, so he may move slower and use smaller steps.