As a practicing chiropractor, I see a large number of patients with neck pain that begins to affect one or both shoulders. Frequently, the opposite occurs as well where a shoulder injury aggravates the neck.
Many conditions of the neck and upper back affect the shoulder and visa versa. There is a good reason for why this happens and I will use this article to explain it.
There is that old statement regarding the human body that goes something like "everything is connected", of course in this instance we are talking about anatomy - specifically a kinematic chain.
In a kinematic chain, the function / health of adjacent joints are dependant on each other. A simple example of a breakdown among joints in a kinematic chain and the resulting consequences would be as follows; a person sprains their ankle, limps on that ankle for several days and then develops knee pain secondary to the limp caused by the injured ankle. If the limping or gait impairment continues for any period of time, the irritation can involve the hip and eventually the low back. The ankle, knee, hip, sacroiliac joints and the joints of low back all form a kinematic chain.
In a similar yet more complicated kinematic chain, the vertebra of the cervical and thoracic spine are intertwined with the shoulder joints. The shoulder is made up of a series joints that allows for a tremendous amount of movement in a number of planes.
Compared to the knee, for example, that only allows for about 120 degrees of flexion and very little rotation and translation, the shoulder is incredibly mobile. While, like the shoulder joint has ligaments and a joint capsule that tie the humorous to the scapula and the clavicle, the primary source of stability of the shoulder joint is the muscles, many of which attach into the cervical and thoracic vertebra.
Regarding the spine - in particular the cervical and thoracic spine - the joints found in the spinal column have considerably less motion than do most other joints in the body. That being said, the cervical spine displays the greatest amount of motion found in the spine while the thoracic spine is the most limited in its flexibility. The fact that many of the big muscles of the neck and upper back insert onto the scapula and the clavicle links these two joint complexes together.
In many cases, shoulder pain or dysfunction can result in spasms of the larger muscles that act to stabilize the shoulder - most of these muscles originate from the vertebra of the neck and upper back. The stress of this spasm can cause pain or dysfunction in the neck and upper back. Because of the shared muscles between the neck, upper back and shoulder girdle, the exact opposite scenario can occur with a primary spinal problem causing muscle spasms that have a negative effect on the shoulder.
Both the shoulder and the neck joints display complex, compound movements. Adjacent joint complexes like these that share major muscle groups make for an increased likelihood of pain / dysfunction affecting more than one group of joints.
In my practice, the two most common activities that I see that lead to pain / dysfunction of the neck and shoulder are computer work and single sided sports injuries like pitching, bowling, golf, etc. When confronted with neck and shoulder pain, I advise my patients to apply ice packs to the affected area in 20 minute sessions at least twice daily and limit the offending activity for two or three days. If the joint is not dramatically better with this at home management, get in to see a chiropractor. Chiropractors are specialists in joint biomechanics and can help you make a complete recovery.