These are just abnormalities that go beyond normal age-related slowing.
But what is normal? Past age 60, walking speed diminishes 1 percent per year. The maximum speed a person CAN walk also declines even faster. If a person walks considerably slower than normal for his or her age, or if he or she shows difficulty maintaining balance while walking or getting going (taking that first step), there could be a gait disturbance.
Geriatricians have ways of measuring a person’s gait. The average size of the step, the steps per minute, and breadth (horizontal distance between feet), can be measured and compared to norms. It may surprise you to learn this, but walking patterns are routinely controlled at the level of the spinal cord, not the brain. Your brain can override the autonomic spinal rhythm generators but without conscious effort, the below-the-neck body walks in its own pattern.
Different gait abnormalities manifest different ways. Most of one or more of these characteristics:
The International Classification of Diseases lists gait abnormalities at R26. There are functional (psychogenic) movement disorders (FMDs) and organic gait disorders.
The University of Missouri has a webpage that lists tests for gait evaluation.
The antalgic limp is the most common limp and happens when a person adjusts to pain in the knee or legs. The gait is asymmetrical so the person spends less time with weight on the affected leg than on the healthy leg. People with arthritis sometimes adopt an antalgic gait.
Slow walk and almost off-balance but with normal range of motion in legs. https://jnnp.bmj.com/content/73/3/310
Abnormal gait formed by weakness or partial paralysis in one leg. Often forms after a stroke. Stroke victims often have a paretic leg and a non-paretic leg.
One leg functions fairly normally while the other is stiff, causing the foot to be dragged along in a semi-circular pattern.
Diagnostic criteria include psychiatric symptoms.
Often seen in people with Parkinson's. Slow walking and shuffling (not picking feet much off ground and small steps).
Not-so-official gaits you might run into include the Magnetic gait in which the person appears to have feets stuck to the floor and able to move only through shuffling and Waddling which means walking like a duck. Dyskinetic is an adjective applied to walking accompanied by involuntary movement.
Problems in walking degrade quality of life and are a visible indicator of aging so much that some people find them embarassing. People with disabled mobility are much more likely to experience depression, social isolation, and falls than the general public. The US government says almost three-quarters of those past age 85 have difficulty walking.
The National Council on Aging has a webpage on fall prevention.