The worst disability occurs when both sense organs and CNS structures are damaged simultaneously. Physical activity is very important for recovery from injury to the sensory systems. The general debility of aging can negatively affect recovery if it results in a decreased level of activity. Diseases of the eyes, such as glaucoma and cataracts, decrease visual sensory function and are a common problem in old age. Injuries to the knees, hips, and back often do not completely heal, leaving some limitation of motion.
Arthritis can cause permanent crippling, non-reversible effects.
Osteoporosis leads to bone weakness and increases the probability of serious injury from a fall, or might cause a spontaneous fracture and lead to a fall. Muscle strength gradually decreases with age. Joint tendons and ligaments lose their flexibility and limit motion. The combined ravages of bone and joint injury, arthritis, and inactivity can result in a body which cannot carry out motion commands initiated by the brain. As many of the problems responsible for falling develop during early and middle age, initial efforts to prevent injuries must be aimed at younger age groups.