Raymond Thal, M.D., in his fifth season as orthopedic specialist for the Redskin, is an orthopedic surgeon at Reston Hospital Center in Virginia.

1. Shoulder pain can be from an acute (single) injury or, more commonly, from repetitive, overuse conditions. It's important that patients understand the difference between the two.

2. Examples of overuse conditions are rotator cuff injuries (tendinitis, tears, etc.) and labrum tears, such as baseball pitchers frequently experience.

3. Shoulder problems occur most frequently in patients over the age of 40 and the most common shoulder conditions are related to the rotator cuff.

4. The rotator cuff is actually a group of tendons attached to four muscles. Treatment may involve anything from rehabilitation to surgical repair of torn tendons. Rotator cuff tears are most common in a person's dominant arm but can also be present in the non-dominant shoulder.

5. The shoulder joint is the body's most mobile joint. Although it can in move in many directions, such capabilities also make your shoulder joint relatively easy to dislocate.

6. Shoulder dislocations and subluxations are common acute injuries. With a subluxation (partial dislocation), the head of the upper arm bone (humerus) moves partially out of the socket. With a dislocation, the humerus moves completely out of the socket. A significant injury is usually required to cause a shoulder dislocation or subluxation.

7. Shoulder pain can result from arthritis, generally stemming from wear and tear changes in the joint. These changes can cause inflammation of the joint, with swelling, pain and stiffness. Sports or work injuries can be the cause.

8. People tend to avoid shoulder movements, in hopes of lessening their degree of pain. This can be counterproductive. It can lead to tightening or stiffening of the soft tissue near the joint, causing more pain and further restriction of movement.

9. With a shoulder separation, the collar bone (clavicle) separates from it's attachment to the shoulder blade (scapula) on the top of the shoulder in a small joint called the acromioclavicular (AC) joint. The ligaments that hold this joint together are torn with this injury.

10. If a shoulder separation is suspected, your physician most likely will X-ray both shoulders to gauge the extent of the damage to the injured one. You may be asked to hold a 10-pound weight. This can help make your injury more noticeable on film.

11. Impingement, one of the most common causes of pain in the shoulder, results from pressure on the rotator cuff. The rotator cuff pinches against the acromion (part of the shoulder blade or scapula) as you lift your arm.

12. Overuse injuries can sometimes be prevented with proper training techniques and appropriate rotator cuff conditioning exercises.