The Body is a Unit
You may have wondered - why does my foot/shoulder/hip/low back hurt? What is the source of the problem and what can I do about it? Most people assume that if the shoulder hurts, the shoulder is to blame, but many experienced therapists have cautioned against this assumption. In fact, a world famous therapist named Karel Lewit said that he who treats the site of pain is lost. Why is this?
In trying to understand why a certain joint is sore, it is helpful to take the perspective that the body is a whole, and that everything in the body affects everything else. A useful analogy is that the body is like a team composed of many different players performing fabulously coordinated actions. If any team member is compromised in its ability to move or stabilize, additional demands are placed on other team members which causes impaired function and increased susceptibility to pain and injury. In other words, each joint is so intimately related to every other joint that if any one joint has a problem performing its functions, this affects the functioning and performance of almost every other joint.
Let's say you want to move your spine to twist or bend. In a healthy coordinated spine, each of the 24 vertebrae in the spine will move a little (some more than others) to accomplish the desired range of motion. The movement will be experienced as easy and smooth. If on the other hand one or more of the segments have lost their ability to move, through lack of use or poor coordination or sensory motor amnesia, other vertebrae will be asked to move further and work harder to accomplish the desired movement. The movement will be experienced as stiff and awkward. The overworked vertebrae may exceed their normal range of motion, which over time could cause pain.
The above example, although very common, is extremely simple. The interactions of the body are extraordinarily complex, and extend from head to toe. So imagine you have injured your big toe and now try walking without moving it at all. You will notice a very pronounced limp which affects the movement of almost every joint in your body. You will notice that your right side is moving very differently from the left, particularly in the hips and even the shoulders. This means that improper function of the big toe can affect functioning of the shoulder.
Does this mean that the shoulder will now be injured? Probably not. But the shoulder now has an extra job it didn't have before – it must do work to make sure the big toe doesn’t bend during walking. As the amount of compensations in the body increase, the demands on each joint increase, and the options for safe and easy movement decrease. At some point, the amount of work placed on a particular joint exceeds its adaptive potential or capacity for safe movement, and pain results The point to remember is that a problem at any joint increases the demands on all other joints to at least some degree.
Yet another example. Let's say you have pain in your foot along the arch. Maybe the problem is a fallen arch. However, the fallen arch might be caused by actions at the hip. If the hip for some reason likes to stay in internal rotation too much, the leg spins inward, which will naturally cause the foot to pronate and the arch to collapse. (Try it, rotate your leg inward and you will notice the arch starting to collapse – spin it out and the arch increases.) It is also possible that the hip wants to internally rotate because for some reason this helps protect the low back from a position that causes it pain. And so on. The point is that the interactions of the body are so incredibly complex, it is often not possible to identify the exact cause of a pain complaint.
So, why does your shoulder hurt? Unless there's knife sticking into it, you will probably never know. But you do know that a coordination problem at almost any other joint could be contributing to the problem. Although this sounds pessimistic, remember that the converse is also true - improvement of the functioning of any joint can cause improvement of the functioning of any other joint. This is an easy way to treat a sore shoulder - improve the functioning of other nearby joints and even far away joints and thereby decrease the demands on the shoulder.
This is why it is a good idea to work on mobilizing and coordinating ALL the joints in the body, not just the ones that are drawing our attention.