Why Do We Stiffen Up as We Age?

No single factor explains such stiffness, said Dr. Mark S. Lachs, director of the Center for Aging Research and Clinical Care at the Weill Medical College of Cornell University. “Morning stiffness should not necessarily be ascribed to ‘normal aging,’ as it could be a symptom of treatable conditions that become more prevalent as we get older,” Dr. Lachs said.

Yet, he said, age-related changes in joint cartilage, combined with a decrease in the amount of lubricating joint fluid it produces in conditions like osteoarthritis, do probably contribute to stiffness. With sitting or sleeping, joint fluid is less evenly distributed in the joint space.

On resuming activity, the cartilage surfaces at first rub against each other without ideal lubrication. As activity continues and lubrication improves, the structures glide with less friction. An analogy is applying a drop of oil to a stubborn gate and then opening and closing it until it stops squeaking, Dr. Lachs said.

Another factor is changes in bone architecture with age. In infancy, supporting structures like ligaments, tendons and the muscles attached to them are relaxed and flexible, but tend to become less so with age, he said. Sitting for long periods keeps such structures maximally contracted, but as the day wears on, the stretching associated with normal activity or exercise can provide some relief.

Patterns of stiffness in specific joints at specific times of day can be clues to certain rheumatologic conditions, Dr. Lachs said, and should be brought to the attention of a doctor.

From the NY Times.