It seems like a no-brainer... My shoulder hurts, so the issue must be in the shoulder. I see so many patients who come in for various forms of body pain where the pain actually has nothing to do with the area of the body where they feel the sensation. This is due to the wonderful world of dermatomes; the areas of the tissue/skin that are supplied by a single nerve root of the spinal cord.
At the base of each vertebra are two nerves, one on each side, that leave the spinal cord and innervate a specific portion of the body. These nerves pass through a small opening called a foramen, which is kept open by the thickness of the spongy disc between the two vertebrae. The figure below shows the dermatomes and their vertebral origination.
As you can see, the majority of the arms are innervated by the cervical spine, the trunk of the body by the thoracic spine, and the waist and legs by the lumbar and sacral spine. As long as enough space exists between the vertebrae, the nerve will be healthy and happy. The trouble starts when narrowing of the foramen happens and the nerve becomes impinged. Narrowing can happen naturally through the normal wear and tear of the discs with aging, by some sort of trauma to the spine, with disc herniation, or through abnormal wear of the discs due to bad posture, arthritis, or any number of other degenerative diseases.
If the impingement is acute, due to an injury or compression from tense connective tissue, you will feel pain in the subsequent region, but resolution can be fairly quick. Let's say that the issue is with the nerve at the base of the 7th cervical vertebra. One quick note on the numbering of the cervical roots- since there is a nerve that exists above the 1st cervical vertebra, there are actually 8 cervical nerves for the 7 vertebrae of the cervical spine. So the nerve in question at the base of the 7th cervical vertebra is labeled C-8. Ok, if C-8 is being impinged on a relatively healthy individual, they will experience acute pain that can be in the shoulder, the ulnar (inner) side of the arm, and down into the pinky and ring finger. This pain will worsen with movements that further squish and aggravate the nerve, and will be relieved when pressure is removed. Acupuncture, tuina, and chiropractic can quickly and effectively relieve pain of this sort by targeting the muscles and ligaments surrounding the vertebrae, thereby releasing the compression, and by helping to calm the inflammation of the nerve.
With chronic degeneration, there will often be changes to the bone in the form of abnormal growth around the foramen or the development of bone spurs. These bony abnormalities will compress and irritate the nerve, often causing severe pain that will not let up. When the problem has progressed to this level, there are still some treatment options that will help to minimize the amount of pain that is felt, but nothing outside of surgery can remove the extra growth on the vertebrae. Patients will often notice a vast improvement of symptoms with a series of treatments, but full resolution is often not possible.
This is why spinal health is so important for longterm quality of life. Regular treatments by a quality acupuncturist or chiropractor, along with proper posture and exercise, will help to keep your spine (and its nerves) operating at an optimal level.