Shoulder pain at night, pain when lifting a briefcase, pain with overhead activities -- even pain while brushing your hair can be caused by shoulder impingement.
To understand shoulder pain, you first have to know a bit about how the shoulder is held together: In large part by the rotator cuff and acromion.[1] The rotator cuff is made up of tendons from the muscles that lift and guide shoulder motion.[2] The acromion is the bone on top of the shoulder; it acts as a roof to the shoulder joint.[3] When the space between the tendons and the bony roof narrows--which can be caused by bone spurs or inflammation--impingement occurs. The pain of impingement comes from the four tendons of the rotator cuff muscles impacting against the underside of the acromion.[4] Think of it as putting a tack between your belt and your waist. Every time you stick your stomach out, the pain occurs.
Figuring out the cause of the impingement drives the treatment. If the acromion has formed a spur beneath it--from arthritis or trauma--removing the spur fixes the impingement.[5] If the lining of the tendons becomes inflamed from repetitive overhead activities, such as pitching or tennis, shrinking the lining solves it.[6] If the mechanics of the shoulder are poor, due to one muscle or another being weak (like a car whose tires are soft on one side), the shoulder moves abnormally, pinching the tissues. Strengthening those muscles solves that problem.
The key is to figure out what the cause is, and to avoid damaging the structures when trying to repair them. A careful physical exam with a good history taker often makes a full, accurate diagnosis. Each muscle can be tested individually, and the point of impingement is usually felt. A high quality x-ray and MRI can differentiate between bony impingement and soft tissue swelling or tearing. (Unfortunately the x-rays or MRIs are often not of sufficient quality to make the best diagnosis. Technique matters.) Sometimes selective injections of the various tissues with short-acting anesthetics can be helpful, though they're usually not necessary.
Impingement is so often caused by specific activities, or imbalances of the shoulder, that a careful physical therapy and strengthening program repairs the damage in most cases. "Careful" is emphasized because we often see the wrong exercises being done, due to lack of an accurate diagnosis. Injections of growth factors and/or stem cells are replacing cortisone in our practice, as they act as a natural anti-inflammatory, stimulate healing and do not have cortisone's downside of weakening the tissues.[7,8] Surgery to remove the spurs or chronically swollen bursa is almost always curative, but it's usually reserved for patients who fail our non-operative approaches.
Life with shoulder pain is not fun. Fortunately, the most common causes are completely fixable.
1.Andrews, James R., William G. Carson, and Kenneth Ortega. "Arthroscopy of the shoulder: technique and normal anatomy." The American journal of sports medicine 12, no. 1 (1984): 1-7.
2.Clark, J. M., and DT 2nd Harryman. "Tendons, ligaments, and capsule of the rotator cuff. Gross and microscopic anatomy." The Journal of Bone & Joint Surgery 74, no. 5 (1992): 713-725.
3.Terry, Glenn C., and Thomas M. Chopp. "Functional anatomy of the shoulder." Journal of athletic training 35, no. 3 (2000): 248.
4.Fu, Freddie H., Christopher D. Harner, and Alan H. Klein. "Shoulder Impingement Syndrome: A Critical Review." Clinical Orthopaedics and Related Research 269 (1991): 162-173.
5.Cone 3rd, R. O., D. Resnick, and L. Danzig. "Shoulder impingement syndrome: radiographic evaluation." Radiology 150, no. 1 (1984): 29-33.
6.Neer, Charles S. "Anterior acromioplasty for the chronic impingement syndrome in the shoulder." The Journal of Bone & Joint Surgery 54, no. 1 (1972): 41-50.
7.Escamilla, Rafael F., Todd R. Hooks, and Kevin E. Wilk. "Optimal management of shoulder impingement syndrome." Open access journal of sports medicine 5 (2014): 13.
8.Foster, Timothy E., Brian L. Puskas, Bert R. Mandelbaum, Michael B. Gerhardt, and Scott A. Rodeo. "Platelet-rich plasma from basic science to clinical applications." The American journal of sports medicine 37, no. 11 (2009): 2259-2272.