Joint Changes as We Age

In 1996 Tracy Lawrence released his classic song “Time Marches On,” a song based around the premise that everything changes. This rings true on many different levels. Today I want to focus on the march of time on the joints of the body specifically. 

In the realm of the connective tissue surrounding the joint, we see a few things happen. First, we first see a slowing down of a cell's ability to grow and divide. This means we have a slower turnover of cells. We then see changes in what is called matrix cross linking, essentially the way the tissues heal is more disorganized than in younger individuals. We also see an increase in fatty substances inside of cells which impairs their ability to carry out their functions, so things like metabolic waste products accumulate in the joint tissues. 

For bones, we see a few distinct things as well. We first see less total bone. Bone is a dynamic tissue that is constantly replenishing itself. As we age this process slows down and we break down more bone mass than we grow. This leads to thinner and weaker bones. We also see bone growing in joint spaces. This is in response to what is called Wolfe’s Law. Essentially as we continue to stress a tissue, the body will lay down new bone to help reinforce the area. This can be seen on images as bone spurs or jagged or uneven joint spaces. 

Next we come to cartilage. Cartilage is the tissue that lives on the ends of bones and interfaces through a joint with the next bone end also lined with cartilage. As we age, cartilage becomes thinner. This is in part due to the slowing of cell function and the inability to keep up with break down. At the same time, the fluid inside the joint is also undergoing changes. Hyaluronic acid makes up a significant portion of the synovial fluid in joints and as we age the size of the hyaluronic acid molecules decreases impacting the fluid's ability to lubricate the joint and cushion it against movement. 

All of these changes can be seen in the slow decrease of total motion that a joint can do as we age. This reduction in motion is highly variable. It can in part be from lifestyle factors or activity. It is not the same reduction across all joints or at the same rate in all individuals. Motion loss can be mitigated through intentional exercise and work. 

So what does all of this mean for us as we age? It actually means very little. When these changes are seen on images in an individual who is no longer a child, it becomes very difficult to determine if those changes are an issue since they are occurring in everyone. We know that pain and disability are massive multifactorial issues and for them to be completely attributed to the natural aging process is a falsehood. Sometimes these changes can be an issue, this is where a detailed exam of an issue, combined with a thorough trial of care is necessary. 

This is where we, as individuals who will inevitably age, must be diligent in the care of our body. We need to do activities to help maintain bone mass, muscle mass, muscle strength, and joint mobility. We will age, and some changes that go along with it are going to happen, so we must set our sights intentionally to keep ourselves healthy and functional.