The basic cause of a winged scapula is muscle weakness and/or muscle imbalances, but there is a tremendous variation in the degree of weakness and imbalance, and in the cause of the weakness and balance.
Two major muscle groups on your back are opposed by muscles on the front of your shoulder. They work together to hold your scapula in the correct position.
"they can contribute to a winged scapula"
The anterior deltoid and pectoral muscles in the front must coordinate with the trapezius and serratus interior muscles in the back, to position the scapula correctly.
Scapular winging develops when there is weakness of the serratus anterior and trapezius muscle groups. When the pectoralis muscles are overdeveloped, or short and tight, they can contribute to a winged scapula.
"weakness in the trapezius and serratus anterior muscles"
Mild scapular winging may develop with activities that constantly strengthen the chest muscles. Athletes who swim or throw may develop mild symptoms when the anterior muscles over power the back muscles.
More commonly symptoms develop because of weakness in the trapezius and serratus anterior muscles. If you spend long hours at a computer or other sedentary work, and do not participate in activities that put your shoulder through a full range of motion, you may be prone to this condition.
"scapular winging can be corrected with simple exercises"
Fortunately when you have a winged scapula from a lack of activity, or a lack of the correct activity, your scapular winging can be corrected with simple exercises.
The second most common cause of a winged scapula is damage to the nerves that control these two muscle groups. If the long thoracic nerve is injured there may be weakness or paralysis of the serratus interior. If the spinal accessory nerve is injured there may be weakness or paralysis of the trapezius muscles.
"nerve injuries may occur from trauma, disease, or as a complication of surgery"
These nerve injuries often go unrecognized and scapular winging may take months to develop. Because proper motion of the scapula requires both the serratus anterior and trapezius muscles, when one muscle group is weak the other muscle group will gradually stretch and become weak allowing the scapular winging.
These nerve injuries may occur from trauma, disease, or as a complication of surgery:
Closed trauma may cause compression due to swelling, stretching, or direct force to the nerves. Penetrating trauma may sever the nerve.
Viruses may affect the nerve as well as other neural diseases such as Parsonage-Turner syndrome.
Surgery on the upper chest and neck, such as breast cancer surgery, may cause may cause temporary or permanent injury to the nerves.
"After an injury these nerves will sometimes regenerate..."
All of these different possible nerve injuries have a wide range of possible outcomes. After an injury these nerves will sometimes regenerate over 18 to 24 months following the acute injury.
In some cases the nerve may heal, the muscle can get strong again, and scapular motion will return to normal.
In other cases you may have a partial recovery of the nerve, leading to partial use of the muscle and only mild scapular winging.
"permanent paralysis of the serratus anterior and trapezius muscles"
When you have permanent and severe damage to the nerves there may be a permanent paralysis of the serratus anterior and trapezius muscles. In these cases some centers will consider surgery involving various combinations of fascial graft and/or transfer of adjacent muscles to control scapular motion.
If you have a mild winging you can start a home exercise program to see if it makes a difference. But, if your symptoms are more severe and you are unable to function, you need to be seen by your doctor.
"tests to evaluate the nerves"
He can order special tests to evaluate the nerves. If the nerves are functioning correctly, he will start you on an exercise program to strengthen weak muscles, or refer you to a physical therapist.