The three main causes of chronic (long standing) shoulder pain are Impingement Syndrome (from the Rotator Cuff)-72%, Adhesive Capsulitis (Frozen Shoulder)-12% and Bicipital Tendinitis-6%. The other 10% are from rare problems that are not obvious such as a missed fracture or bone tumor. Of course this assumes that you went to a good doctor that has ruled out a pinched cervical spinal nerve or one of the several shoulder bursas that can become inflamed. The main source of impingement is where the insertions of the Rotator Cuff tendons enter onto the head of the upper arm bone (humerus) from the scapula. There are only narrow conduits for the muscle/tendon to enter and exit. With damage to these insertions such as injury or tear of the tendon/muscle they are unable to slide through that narrow space without a slight hang-up that produces anything from discomfort to pain or distinct inability to do that required motion.
The rotator cuff is made up of four muscles from the scapula. The rotator cuff helps to lift and rotate the arm and to stabilize the ball of the shoulder within the joint. The rotator cuff is made up of four muscles and their tendons. These combine to form a " cuff " over the upper end of the arm (head of the humerus). These are the Supraspinatous, Infrascapular, and the Terres Minor on the back side and the Subscapular on the underside of the scapula. Depending on the specific tendon involved there are 5 different anatomical sites that are impinged. The most common is with damage to the end of the Supraspinatus muscle. The pathology varies from just swelling of the tendon (Stage I) to a partial tear (Stage II) to a full tear (Stage III). Usually Stages II and III are related to acute trauma and commence right after the injury, while Stage I is due to overuse of that muscle group in overworking that muscle such as pitching or repetitive light weight lifting. Usually these problems occur in folks over the age of thirty.
Some of the signs of a rotator cuff tear include:
• Atrophy or thinning of the muscles about the shoulder
• Pain when lifting the arm
• Pain when lowering the arm from a fully raised position
• Weakness when lifting or rotating the arm
• Crepitus or crackling sensation when moving the shoulder in certain positions
Symptoms of a rotator cuff tear may develop right away after a trauma, such as a lifting injury or a fall on the affected arm. When the tear occurs with an injury, there may be sudden acute pain, a snapping sensation and an immediate weakness of the arm. Symptoms may also develop gradually with repetitive overhead activity or following long-term wear. Pain in the front of the shoulder radiates down the side of the arm. At first, the pain may be mild and only present with overhead activities, such as reaching or lifting. Over the next several weeks, it is present when just moving the shoulder. The patient, however, has no problem lying on their shoulder in bed.
A pinched cervical nerve has more of a burning sensation and is brought on by moving the neck rather than the upper arm.. It also has a specific nerve root anatomic distribution called a dermatome noted on many charts of which one is up on your doctors wall. A specific test is a nerve conduction study or maybe an MRI of the neck which has as many false positives as negatives. The test that I recommend is a “drag pin exam” where the observer takes a safety pin and drags it lightly over the affected area of pain manifestation, the dermatone, and more “friction” is noted on the pin at the same time the patient feels an accentuation of the discomfort. Very rare problems such as thoracic outlet syndrome, or brachial plexus injury will take more studies to confirm, but can be usually ruled out by a good history of the cause and the symptoms. With the bursitis, the sensitive spot is directly over the anatomical location. Also movement of the arm will increase the pain at that tender place.
Another shoulder problem is Bicep Tendenopathy where this structure is damaged due to trauma and occurs acutely in people under the age of 30. Most likly there is a labial tear in the Gleno-Humeral junction. This results in instability of the shoulder joint and can lead to dislocation of the shoulder joint. When the arm is extended by the observer, immediately the patient feels this is an impending problem and will wince or push the observers hand away lest his shoulder will come out of the socket. In older people, the tendon may rupture and a “popeye” muscle will occur. In the past these were operated, but now we leave them be and they generally resolve with the knot shrinking over the years and only a small loss of bicep muscle strength. The other head of the biceps takes over.
Capsulitis or frozen shoulder is usually the result of unresolved tendon impingement. Rehabilitation with physical therapy helps, but they will never be as good as new. Certainly surgery is not the answer in that their rehab will be more prolonged and not as successful. Next week we discuss the magic of a shoulder injection.