Older adults do get "out of shape" as the pain of arthritis slows them down. Deconditioning and loss of balance leave a person feeling uncertain of his or her ability to do a task or activity.

Walking, going up and down stairs, and getting up from a seated position without using the hands are three measures used to assess function. These tasks can be affected by knee pain, loss of muscle strength, decreased endurance, or a loss of motion.

The arthritis can contribute to one or all of these losses. An exam is needed to find out for sure the cause of your mother-in-law's problems. A medical exam can help rule out other important causes of this downward decline.