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The shoulder joint is a ball-and-socket joint. The head of the humerus (upper arm bone) is the ball and the scapula (shoulder blade) forms the socket.

The scapula and arm are connected to the body by multiple muscle and ligament attachments. The front of the scapula (acromion) is also connected to the clavicle (collarbone) through the acromioclavicular joint.

As you move your arm around your body, your scapula must also move to maintain the ball and socket in normal alignment.

(Left) The bones of the shoulder. The scapula serves as a site for the attachment of multiple muscles around the shoulder. (Right) The muscles and soft tissues of the shoulder.

Reproduced from JF Sarwak, ed: Essentials of Musculoskeletal Care, ed. 4. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2010.

This photo shows a patient with a "winged" scapula (arrow). Note the prominence of the medial (inner) border of the bone.

Disorders of the scapula result in a deviation, or alteration, in the:

• Normal resting position of the scapula, or
• Normal motion of the scapula as the arm moves

The medical term for these alterations is scapular dyskinesis ("dys"= alteration of, "kinesis" = movement).

In most cases, alterations of the scapula can be seen by looking at the patient from behind. The medial (inner) border of the affected shoulder blade will appear more prominent than the one on the opposite side. This prominence (bump) will often be exaggerated as the patient moves their arm away from the body. This is commonly called a "winged" scapula.

Causes of scapular dyskinesis include:

• Weakness, imbalance, tightness, or (rarely) detachment of the muscles that control the scapula
• Injuries to the nerves that supply the muscles
• Injuries to the bones that support the scapula or injuries within the shoulder joint

The most common symptoms of scapular dyskinesis include:

• Pain and/or tenderness around the scapula, especially on the top and medial (inner) border
• Weakness in the affected arm — your arm may feel tired or "dead" when you try to use it vigorously
• Fatigue with repetitive activities, especially overhead movements
• Limited range of motion — you may be unable to raise your arm above shoulder height
• A crunching or snapping sound with shoulder movement
• Noticeable protrusion or "winging" of the scapula
• A drooped or forward tilted posture on the affected side

In some cases, the symptoms of scapular dyskinesis may improve with simple home treatment that includes:

Restoring good posture. As you perform your everyday activities, try to stand and sit properly. To do this, pull your shoulder blades back together, and bend your elbows down and back as if you are trying to put them in your back pockets.

Balancing your exercise routine. If you are in a regular exercise program, make sure your upper body strength sessions are balanced. For every set of "presses" that you perform, you should do one set of "flys" and two sets of "rows." Your program should also include stretching exercises for your front shoulder muscles and for shoulder joint rotation.

Heat therapy. Soaking in a hot bath or using a heating pad may help alleviate tight shoulder muscles.

If your symptoms persist, it is important to contact your doctor. They can help determine the exact cause of your dyskinesis and provide treatment options.

Once the causes of your dyskinesis have been addressed and normal scapular position and motion are restored, your doctor may recommend a maintenance conditioning program of flexibility and strengthening. This is especially important if your job or recreational activities involve vigorous or repetitive shoulder and arm movements. These exercises should be done 3 times a week or as recommended by your doctor.