Compensation simply means that our bodies are too good at adapting. Like water, following the path of least resistance, our bodies look for the easiest way to accomplish a task.
We compensate in favor of the forces in our lives so we can keep doing what we need and want to do. Compensation causes us to change the way we perform a motion to make it easier due to the presence of some kind of barrier. Whether that barrier is pain, muscle weakness, or a limited range of motion, we alter our movement patterns to get around it.
For instance: if you step on a thorn, your body immediately begins to shift where those weight-bearing forces are directed in an effort to avoid pain in the bottom of the foot. (In this case, pain is the barrier to normal movement.) You then take to limping rather than letting your weight sit normally through your foot. Our body does this naturally, but often in ways that are not always as obvious as a limp.
If we are so good at adapting and compensating, why is this bad? Simply because when we compensate, it means that we change the natural or most correct way our body responds to the forces in our lives. Most people understand that limping makes you less efficient or slower; over time, it can even develop into knee or hip pain.
I see this all over the body–in knees, shoulders, feet, hands, and especially in backs. Backs are often weak, and yet they often compensate for weakness until a bulging disc occurs or pain is too great. Shoulders are predisposed to injury due to weakness in the rotator cuff.
This is why, when left to ourselves, sometimes our bodies will not heal–or not heal correctly. There is too much natural compensation, avoiding of barriers, pain, weakness, and loss of range of motion. It is just too easy to take the path of least resistance so our body never rises to the challenge of overcoming the barrier causing the limitation.