Here we have a 12 year old baseball player that experiences shoulder pain when pitching. His shoulder flexion is 123 degrees and ideally should be closer to 180 degrees. As he raises his arms overhead the arch in his lower back increases quite a bit. This is the compensation program the brain has selected in order to get the hands higher in the air. Due to the insufficient flexibility of the shoulder the hands can only get so high, the brain knows more height can be achieved if the lower back arches.
The tight muscles of the shoulder not only put the shoulder at risk for injury, as demonstrated by our subject experiencing pain when pitching, but also contribute to generating excessive motion in the lower back. Over time this added motion to the lumbar area can create unwanted wear and tear to the joints and discs, leading to inflammation, irritation and potentially arthritis.
Fortunately this athlete doesn't have lower back pain, yet. If he did I would not treat his back, I would treat the true source of the problem, his shoulder. I would put him on a flexibility program focused on his shoulders and thoracic spine (mid-back). The result would be he could reach overhead without engaging his lower back.
This is a perfect example of how an issue in one area of the body can cause a problem in another part of the body. Again most conventional therapy approaches would have focused on his lower back and because the true source of the problem was not addressed he would have seen very little improvement in reducing his pain.
Shoulder Restriction Leading
to Lower Back Pain..
In photo 1 you can see if we don't allow our subject to extend her spine she achieves an angle of 144.6 degrees of shoulder flexion.
In photo 2 we allow the subject to extend her spine in order to gain a greater reach overhead. Shoulder flexion is now 170.4 degrees. Due to the restricted range of her shoulder, every time she reaches overhead, her back will have to arch. This ends up putting more "mileage" on her lumbar facet joints and discs, making them more susceptible to irritation and injury.
Typically most therapies would focus the attention on her lower back if she were complaining of pain and discomfort. As one can see that would not be addressing the source of the problem. Treating the lower back would not increase the flexibility of the shoulder and therefore she would continue to have pain. The solution is directed program of manual therapy and stretching to eliminate the shoulder restriction.