Scapular Dyskinesis

Description

The shoulder blade (scapula) is a flat, triangular bone that floats on the back of the rib cage. It has almost no bony connection to the rest of the skeleton: just a small joint at the collarbone. Everything else that holds it in place and moves it is muscle. Seventeen muscles attach to it, from the big trapezius across the upper back to the small rotator cuff muscles that run to the ball of the shoulder.

Those seventeen muscles work together like an orchestra. When you raise your arm, the shoulder blade has to rotate upward, tilt back, and swing around the ribs, all at the right moment and by the right amount, so the socket stays under the ball. Each muscle plays its part on cue. Scapular dyskinesis simply means the orchestra is out of sync: some muscles fire late, some fire too hard, and the shoulder blade moves wrong. It is not a disease of the bone. It is a timing and control problem, and it is very symptomatic: a shoulder blade that is out of rhythm produces real pain and real weakness in the arm, and it sits behind a great many cases of shoulder pain in young athletes.

How it happens (the mechanism)

Something has to throw the orchestra off. The common triggers:

• A trauma. A collarbone fracture, a sprain of the joint at the top of the shoulder, a shoulder dislocation, or a hard fall. The injury heals, but the muscles have guarded and compensated for weeks, and they do not return to their old pattern on their own.
• Pain from anything. Pain in the shoulder switches off the muscles that stabilize the blade (the lower trapezius and serratus anterior especially) and switches on the ones that hike it up (the upper trapezius). The body does this automatically to protect the joint. Once the pain settles, the pattern often stays.
• Overuse in overhead sport. Pitchers, swimmers, volleyball and tennis players make thousands of arm swings a week. The small stabilizers fatigue first, and the big muscles take over with a cruder motion.
• Tightness. A tight pectoralis minor at the front of the chest tips the blade forward; a tight back of the shoulder capsule pulls it around the ribs. Both change its resting position.
• Posture and growth. A teenager who has grown fast, sits rounded over a screen, and has not yet built the back muscles to match the new frame.

Once the blade moves out of rhythm, it stops presenting the socket properly to the ball. The rotator cuff then works at a mechanical disadvantage, the space under the tip of the shoulder narrows, and the tendons there get pinched during overhead motion. That is why dyskinesis so often shows up as "impingement" or "rotator cuff pain" in a 15-year-old whose rotator cuff is perfectly healthy.

Symptoms

• An ache around the shoulder blade, the top of the shoulder, or the side of the neck, worse at the end of a day of overhead activity.
• Pain when raising the arm, especially between shoulder height and overhead, with a loss of strength or velocity in throwing, serving, or swimming.
• Fatigue in the arm long before the muscles should be tired.
• Clicking, grinding, or snapping along the inner edge of the blade as the arm moves.
• The blade itself looks wrong: it sits lower or further out than the other side, its inner edge or lower tip lifts off the ribs (winging), or it hikes up toward the ear when the arm is raised.
• Sometimes the arm feels heavy or tingly from the blade drooping onto the nerves and vessels that pass underneath.

Doctor examination and imaging

The diagnosis is made by watching. I look at the shoulder blades from behind with the shirt off, at rest and while the arms are raised and lowered slowly several times, and I compare the two sides. Weighted repetitions often bring out a pattern that is hidden at rest. Then I do two simple tests: I hold the blade in a better position while the arm is raised (the scapular assistance test), and I hold it pulled back while testing arm strength (the scapular retraction test). If the pain drops or the strength returns when the blade is helped, the blade is the problem. I also check the tightness of the chest and the back of the shoulder, the strength of each key muscle, and the nerves.

X-rays are normal in dyskinesis and are used to rule out other causes. An MRI is not usually needed.

Treatment

The treatment is rehearsal: teaching the seventeen muscles to play together again. It is almost entirely physical therapy, and it works when it is done in the right order.

1. Loosen what is tight. Stretch the pectoralis minor and the back of the shoulder capsule, and restore extension in the upper back. A blade cannot sit right on a rounded, stiff rib cage.
2. Wake up the stabilizers. The lower trapezius and the serratus anterior are nearly always the quiet sections. Simple low-load exercises teach them to fire: wall slides, scapular clocks, prone Y and T lifts, and the push-up with a "plus" at the top.
3. Rebuild the rhythm. Movements that combine blade control with arm motion, first slowly and then with load: rows, lower-trap raises, and serratus punches, progressing from lying to standing to sport positions.
4. Add the rotator cuff last. Cuff strengthening before the blade is stable just trains a bad pattern. Once the blade holds its position, the cuff work makes the whole shoulder strong.
5. Return to the sport with the fix built in. For a thrower or a swimmer, the coach and the therapist look at the technique that caused the problem.

My home program for shoulder instability and scapular dyskinesis lays these steps out. Pain is managed with activity changes, ice, and occasionally a short course of anti-inflammatory medicine; injections are rarely needed. Surgery has almost no role in dyskinesis itself, only in the rare structural causes behind it, such as a nerve that has not recovered after a year or a bony bump under the blade.

Recovery and long-term outlook

Most teenagers improve substantially in six to twelve weeks of a proper program, and the rest of the shoulder pain often disappears with it, because the impingement and the weakness were downstream of the blade. The program has to keep going, in a shorter form, for the rest of the season, since the old pattern returns with fatigue.

When to call the doctor

Call if the winging is severe or appeared suddenly after an illness, a blow, or a surgery, if there is numbness or weakness in the arm or hand, if the shoulder is slipping out of place, or if there is no improvement after eight weeks of therapy.

Learn more

OrthoInfo (AAOS), Shoulder Pain and Common Shoulder Problems: orthoinfo.aaos.org (opens in a new tab)

My guides to anterior shoulder instability, posterior shoulder instability, multidirectional and global shoulder instability, and the home program for shoulder instability and scapular dyskinesis.

This information is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. For specific concerns about your child, consult a board-certified, fellowship-trained pediatric orthopaedic surgeon.