George F. Fuller, COL, MC, USA from White House Medical Clinic, Washington D.C. provided an article under American Family Physician that one way to screen the elderly is by noting if they have a history of fall within the last 6 months. If an elderly has more than 2x of occurrence of fall within 6 months an evaluation is warranted for any possible underlying problem. This may already denote a declining physical and physiological status.
Now if you like to test the mobility of an elderly, an easy way to do it is the Timed "Up and Go" Test. Wherein an individual is timed from doing this test. The patient sits on a standard armchair, stands up and walks for 3 meters (10 feet), turns around and return to a sitting position.
The individual is freely mobile if done in < 10 seconds; mostly independent if done within 11 to 20 seconds; Variable mobility if within 20 to 30 seconds and Impaired mobility if > 30 seconds. This will help you gauge if your elderly patient or love one has impaired mobility already.
Reference for Timed "Up and Go" Test is found on Table 6 of the link from Sir George Fuller's article under American Family Physician. (Click on the link above)
Next topic will be another way to test standing balance.